C172 Still In Production After 60 Years.

[De_flieger]

Maybe someone with internet skills can compare the 1970 price of a C172 to a similarly priced BMW or Mercedes or John Deere tractor, and recompare the difference to equivalent plant today.

I'll give it a shot.

The 1971 C172 Skyhawk (according to Wikipedia) retailed for $US 14,995.
A new C172, admittedly with glass cockpit avionics and other gadgets, but new from the factory and ultimately doing the same job of transporting two adults and two midgets in moderate discomfort, is listed online from Textron for $US403,000 or so, or roughly 26 times the price of the 1971 model. That works out to just shy of $520,000 Australian dollars today, before you put fuel into the tanks.

The Mercedes 280 SL, which was just what appeared when googling 1971 Mercedes sports car, and apparently was (and remains) a fairly highly regarded sports car, had a new retail price of ~$11,958, just under the price of some of the slightly older C172s, and a new Mercedes sports car, depending on the trimming and model, won't give much change out of $100,000.
A top of the line 1971 Ford Mustang had a sticker price of $US 4124, the new top of the range Ford Mustang comes to around $US 55,000
And in 1971 the US median household income was $US 7956, compared to today- the latest figures I could quickly find were from 2014, $US 53013.

So for a rough guide from 1971 to today, the other equivalent items have gone up roughly ten times in price, looking solely at the number of US dollars being handed over, and the average Australian weekly income went from around $88 per week - $~4580 per year - to around $1145 after tax.

A C172 went from less than two years of average US income, to more than 7 years of average US income, or less than three years of average Australian income to just under 9 years of average Australian post-tax income. If you want a Mercedes, Ford Mustang, expensive yacht or some other luxury toy, you can do it much more affordably than going anywhere near a Cessna, and have $300,000 left in the bank. And on the weekend you can take your car or yacht for a fun drive without checking your medical, licence, ASIC, biennial flight review, night currency, $1400 headset, stopping off to buy new maps and ERSA because the old ones expire every 3-6 months, updating your AIPs, putting $300 in the bank to cover fuel and maintenance for every hour in the air and so on and so forth.

There are probably some minor rounding errors in there, but the gist of it remains:
Ford Mustang, takehome pay, Mercedes sportscar etc are approximately ten times their 1971 prices. The Cessna, 26 times.

[Seagull V]

And now a Drone 172

From latest Avweb


Authoritieson both sides of the border are investigating the apparent ghost plane crash ofa Michigan-based Cessna 172 in a remote area of Northern Ontario. According tothe Wawa News, the plane crashed about 11:30 p.m. about halfway between SaultSt. Marie and Thunder Bay near the north shore of Lake Superior, and there wasno sign of a pilot. Local police reported the plane was empty, there were notracks in the snow, no gas in the tanks and the autopilot was on. The crashsite is about 400 NM from Ann Arbor, pretty close to the full-tanks range ofthe 172.

[Acrosport II]

Originally Posted by De_flieger

I'll give it a shot.

The 1971 C172 Skyhawk (according to Wikipedia) retailed for $US 14,995.
A new C172, admittedly with glass cockpit avionics and other gadgets, but new from the factory and ultimately doing the same job of transporting two adults and two midgets in moderate discomfort, is listed online from Textron for $US403,000 or so, or roughly 26 times the price of the 1971 model. That works out to just shy of $520,000 Australian dollars today, before you put fuel into the tanks.

The Mercedes 280 SL, which was just what appeared when googling 1971 Mercedes sports car, and apparently was (and remains) a fairly highly regarded sports car, had a new retail price of ~$11,958, just under the price of some of the slightly older C172s, and a new Mercedes sports car, depending on the trimming and model, won't give much change out of $100,000.
A top of the line 1971 Ford Mustang had a sticker price of $US 4124, the new top of the range Ford Mustang comes to around $US 55,000
And in 1971 the US median household income was $US 7956, compared to today- the latest figures I could quickly find were from 2014, $US 53013.

So for a rough guide from 1971 to today, the other equivalent items have gone up roughly ten times in price, looking solely at the number of US dollars being handed over, and the average Australian weekly income went from around $88 per week - $~4580 per year - to around $1145 after tax.

A C172 went from less than two years of average US income, to more than 7 years of average US income, or less than three years of average Australian income to just under 9 years of average Australian post-tax income. If you want a Mercedes, Ford Mustang, expensive yacht or some other luxury toy, you can do it much more affordably than going anywhere near a Cessna, and have $300,000 left in the bank. And on the weekend you can take your car or yacht for a fun drive without checking your medical, licence, ASIC, biennial flight review, night currency, $1400 headset, stopping off to buy new maps and ERSA because the old ones expire every 3-6 months, updating your AIPs, putting $300 in the bank to cover fuel and maintenance for every hour in the air and so on and so forth.

There are probably some minor rounding errors in there, but the gist of it remains:
Ford Mustang, takehome pay, Mercedes sportscar etc are approximately ten times their 1971 prices. The Cessna, 26 times.

Yes, quite a substantial increase over the years.
It appears my new price for the base model C172R may be a bit off. That was from Wiki, but the 2012 price.
$400,000USD is high. Not even sure if you can buy a base model now without the EFIS.

Real Shame.


Role Civil utility aircraft
National origin United StatesManufacturer
Cessna Aircraft Company, Reims Aviation (under an agreement)[1]


First flight 1955
Introduction 1956
Status In production
Produced 1956–86, 1998–present
Number built c. 43,000[2]
Unit cost

• 172: US$8,700 (1956)[3]
• 172R: US$274,900 (2012)[4]
• 172S: US$307,500 (2012)[5]

Developed from Cessna 170
Variants T-41 Mescalero

[cattletruck]

If you think a C172 has a huge markup take a look at the list price of an F35.

Normally big manufacturers end up pricing themselves out of the market when fresh competition is allowed to prosper - but in today's world this aint happening because of over regulation and litigation which feeds a lot of non-flyers.

The C172 will probably be in production for another 60 years and by then will cost as much as an F35 costs now.

The alternate pathway to getting into owner/flying is to buy a Fokker Dr.1 kit from the kiwis for $10k, source an aero engine ~$20-50K, and build it yourself.

[Andy_RR]

We should compare the price of C172s with houses, which are equally dangerous should they fall out of the sky and still tend to be made with similar methods to fifty years ago. By using this benchmark the humble Skyhawk will look like very good value indeed!

[rutan around]

onetrack said in post #47

Well, perhaps if some company had the wheelbarrow-sized cojones to introduce robotic manufacturing, the cost of the 172, or its modern equivalent, just might halve - and then more people could afford them, production would increase substantially, and cover the cost of the robotics - and GA might once again flourish.

Well actually there is a close Australian equivalent to the C172 that does have some clever manufacturing advantages over traditional cessnas. eg two men making 5 sets of of wings in 5 days while next door 5 men worked 5 weeks to make a set of similar sized aluminium wings.

This Ozzie aircraft has a better useful load , a wider cockpit , and a lower fuel burn. It does all this with the same or better cruise speed and range of a C172.

It costs $130K - $140 K if built by the factory. Compare that price with $492 K plus freight for the American machine.

What plane is the Ozzie competitor?

A Jabiru of course. Before going ballistic and berating me on this forum look up the specs yourself for the Jabiru J450 and for the Newbuild C172.

[Derfred]

Originally Posted by A Squared

I think that a representative of BMW or any other current auto manufacturer would be surprised to discover that they aren't heavily regulated and aren't subject to lawsuits.

Of course they are regulated and subject to lawsuits (as are the manufacturers of $5 plastic kids' toys), but no-where near to the same extent. Someone quoted 50% of the purchase price of a C172 is now pure liability insurance coverage. That's before any regulation and certification costs.

I don't think 50% of your BMW purchase price would be liability insurance. Of course, we don't know the figure - we only know the Cessna figure because it came out in public to pass new liability laws to allow Cessna to recommence manufacturing.

There have been some high-profile liability cases against auto-manufacturers, but they generally don't kill the manufacturer and send the prices through the roof in the same way they did Cessna. I don't think anyone doubts that Cessna built good, safe aircraft*. It's a shame the legal system effectively killed them.

The only Cessna equivalent to the "modern" Mercedes sports car is the TTx (which Cessna didn't even design) and which costs more than twice a C172. So our 2.6-4.0 ratio (suggested by a couple of posters, thank you for that) then goes up to a factor of 5.2-8.0 or more. And that's in the US. It would be presumably even higher in Australia.

So perhaps we could suggest that in 1970, an average LAME (or any private pilot with a slightly above-average income) with a good savings discipline could have purchased a new C172 after 4-5 years of savings, whereas today it would take them 30-40 years. That aint gonna happen, hence private GA is dead, and enter the rise of the less-safe ultralights, experimental, home-builts etc.

Most automobiles reach the point of diminishing returns between say 12-16 years of age where it becomes cheaper to scrap them and buy a younger one than to maintain them to standard. That's a "good thing", because newer cars are generally safer, so there is a safety benefit in having a certain level of turnover. Commercial RPT aircraft, being built to more industrial standards, still hit that point around 18-25 years.

Yet we persist in flying 50 year old C172's not because we love them but because the new ones are priced out of reach. Is that really the optimum safety outcome the law-makers have been looking for all these years? Or, out of perhaps good intentions, all they have succeeding in doing is stifling innovation, research and development, and manufacture of better and safer aircraft for one and all.

Why? I don't know. But perhaps it is due to the absurd concept alluded to by an above poster that GA needs to adhere to a "zero accident" policy, which is not applied by society to any other private or small-business pursuit that I can think of. Seen a fatal truck accident near you recently? I certainly have. But them $5 kiddy toys have to make the warehouse by morning "or else".

At the end of the day, the only explanation for the current state of affairs is that it's the law-makers' fault. Do they care that they have killed GA? Sadly no. There's the problem, right there.

[onetrack]

After seeing the liability payout figures for Toyota and VW (just to name 2 auto manufacturers) in recent times, the claim that auto manufacturers face no liability claims, falls flat on its face.

You would have to go through the auto manufacturers financial statements with a fine tooth comb, just to try and get an reasonably accurate estimate of what recalls, lawsuits, and civil and criminal penalties have cost them. They sure aren't trumpeting it to the world.

At a glance -

Toyota - US$1.2B in regulatory fines in the U.S. for the "unintended acceleration", Govt punitive action ...
US$3.4B for the "rust in pickups" action ...
Unknown $ figure for the cost of over 10,000,000 recalls in the early years of this century, as Toyota dropped the ball on QC ..
Unknown $ figure for the total payouts in individual "wrongful death" lawsuits and civil class action claims.

VW -

A reputed US$19B in punitive damages ... just in the U.S. alone ...
An unknown number and cost (to me) of VW recalls ...
An unknown figure for financial compensation, for a huge number of VW owners who were deceived by cheating on emission figures ...
An unknown $ cost figure for Australian VW owners, that is yet to hit the courts ..
An unknown $ punitive penalty from the regulatory Australian ACCC if it wins its "misleading and deceptive conduct" case against VW.

There are many other auto manufacturers that have had massive payouts and punitive damages awarded against them.
The fuel tank fire problem with Ford Pintos, the early Ford Explorer rollover problem, the dozens of models with faulty fuel systems that caused fires .. the list goes on.

I would hazard a guess, that the legal fraternity in the U.S. have funded their luxury lifestyles out of the hundreds of millions they have made from auto manufacturer lawsuits alone ...

I guess the simple fact is, that the C172 liability insurance cost factor is purely related to the low number of C172's produced - and the fact that most of the C172 crash lawsuit claims would have been centred around fatalities, and that most of those fatalities would have been wealthy and high-income earners, thus seriously increasing the payouts, as the claims probably took "loss of potential earnings" into account.

Probably what is more interesting, is that there is no similar "liability cost factor" in the price of a Jabiru. I suppose that is partly because the Jabiru has not been in production as long as the C172, and partly because the Jab is a relatively "crashworthy" aircraft with good cabin strength - and partly because Australia hasn't got quite as litigious as the U.S., yet.

[A Squared]

Originally Posted by rutan around

Well actually there is a close Australian equivalent to the C172 that does have some clever manufacturing advantages over traditional cessnas. eg two men making 5 sets of of wings in 5 days while next door 5 men worked 5 weeks to make a set of similar sized aluminium wings.

This Ozzie aircraft has a better useful load , a wider cockpit , and a lower fuel burn. It does all this with the same or better cruise speed and range of a C172.

It costs $130K - $140 K if built by the factory. Compare that price with $492 K plus freight for the American machine.

What plane is the Ozzie competitor?

A Jabiru of course. Before going ballistic and berating me on this forum look up the specs yourself for the Jabiru J450 and for the Newbuild C172.

OK, well, I'll concede that you did have me googling, not being terribly familiar with the Jabiru. Excellent troll, you got me.

Unless wikipedia has misled me, the factory built aircraft do not have standard airworthiness certificates, they are all 2 seat aircraft certificated in the LSA or Primary category.

The J450 you quote as the faster, further with more load and cheaper than the 172 is neither certified in *any* category, nor is it factory built. It's an amateur build kit. Sorry, comparing a kit to a certificated airplane is not an intelligent comparison. It has long been the case that some amateur built planes have been able to outperform certificated aircraft. The reasons for that are various, but it's pretty unlikely that the price is going to survive going through certification with a standard airworthiness certificate and paying the people assembling it.

Have you got an aircraft certificated in the Normal Category which has a larger cabin than the C172, and can go further and faster with more load than the 172 on less fuel at half the purchase price?

[A Squared]

Originally Posted by onetrack

I guess the simple fact is, that the C172 liability insurance cost factor is purely related to the low number of C172's produced -

That's one of the major factors that folks are neglecting from thier economic comparisons. In 2015, cessna sold 143 172s. They sold 539 total aircraft that year. In the US alone, MB sold 4,000 SL roadsters in 2015. MB's US sales are around 25,000 vehicles per month


If MB engineers a new airbag system, they amortize the development costs over hundreds of thousands of units. If Cessna engineers a new seat, those development costs are amortized over, at best, a few thousand units.


Seats come to mind because of an experience a few years back. I was writing for an aviation publication and travelled to Columbia where a new utility aircraft was being developed (The Gavilan, very similar to the AirVan) One of the things I learned while down there was just how big a deal seats were. Part 23 has specifications for crash energy absorption for aircraft seats, and the company developing the Gavilan had spend in incredible amount of money engineering a pilot seat to meet those specs, then demonstrating the seat's ability to meet the specs. Demonstrating that ability was a considerable portion of the cost. I wish I recall the cost I was told as it would make a better story, but I just recall that it was astonishing amount, for something which seemed so simple. In a way, it was the seat costs which sunk the Gavilan. They essentially ran out of development money after designing and getting approval for the seats, and were unable to design and certify passenger seats. As a result the aircraft never received US certification with more than the front seats, which is obviously a pretty significant disadvantage in a fairly large utility airplane.

ANyway, the point being, if you take the large costs of engineering and testing energy absorbing seats, and amortize that cost over very few units, the per unit cost is very high, and is reflected in the price of the airplane. Then you consider that an airplane contains lots of things like the seats which require a lot of money to develop and prove.

[Derfred]

Originally Posted by A Squared

That's one of the major factors that folks are neglecting from thier economic comparisons. In 2015, cessna sold 143 172s. They sold 539 total aircraft that year. In the US alone, MB sold 4,000 SL roadsters in 2015. MB's US sales are around 25,000 vehicles per month


If MB engineers a new airbag system, they amortize the development costs over hundreds of thousands of units. If Cessna engineers a new seat, those development costs are amortized over, at best, a few thousand units.


Seats come to mind because of an experience a few years back. I was writing for an aviation publication and travelled to Columbia where a new utility aircraft was being developed (The Gavilan, very similar to the AirVan) One of the things I learned while down there was just how big a deal seats were. Part 23 has specifications for crash energy absorption for aircraft seats, and the company developing the Gavial had spend in incredible amount of money engineering a pilot seat to meet those specs, then demonstrating the seat's ability to meet the specs. Demonstrating that ability was a considerable portion of the cost. I wish I recall the cost I was told as it would make a better story, but I just recall that it was astonishing amount, for something which seemed so simple. In a way, it was the seat costs which sunk the Gavilan. They essentially ran out of development money after designing and getting approval for the seats, and were unable to design and certify passenger seats. As a result the aircraft never received US certification with more than the front seats, which is obviously a pretty significant disadvantage in a fairly large utility airplane.

ANyway, the point being, if you take the large costs of engineering and testing energy absorbing seats, and amortize that cost over very few units, the per unit cost is very high, and is reflected in the price of the airplane. Then you consider that an airplane contains lots of things like the seats which require a lot of money to develop and prove.

A2... I think your post is kind of my point.

Suppose I own a highly regarded German seat manufacturer, let's call it DasSeat GMBH.

I just googled that to make sure I'm not upsettting anyone and surely enough, there is currently no company named DasSeat GMBH. And no-one with that internet domain name.

Weird. That domain wouldn't last 5 minutes in the US without someone trying to scalp it.

To get back on topic, suppose I am contracted by BMW to make top-of-the-range seats, in comfort and safety. And let's assume that I can and do deliver.

And then Cessna USA contacts me and says "I want those seats, can they do X G's forward, Y G's sideways and Z G's vertical?"

My response might be, "Yes we can do that specification both forward and sideways, but not the vertical because BMW never needed that cert".

So then Cessna says "great, just cert them for Z G's vertical and we will buy 2000 of them.

Response: "I'm sorry, your message got cut off. Did you want 2 million, or 2 hundred thousand."

Cessna: "No, 2 thousand".

"We are a wholesaler not a retailer, I suggest you go to Walmart".

[Band a Lot]

Have you got an aircraft certificated in the Normal Category which has a larger cabin than the C172, and can go further and faster with more load than the 172 on less fuel at half the purchase price?


No but a few short years ago in a rough ball park price the Gippsland Aerospace GA8 was certified Normal Category.



Top speed: 241 km/h

Cruise speed: 222 km/h


Weight: 1,014 kg


Range: 1,352 km


Wingspan: 12 m


Unit cost: 699,000–699,000 USD (2013)


Engine type: Lycoming O-540


__________


Range: 1,185 km

Top speed: 302 km/h


Cruise speed: 226 km/h


Wingspan: 11 m


Length: 8.28 m


Engine type: Lycoming O-360


Unit cost: 364,000–364,000 USD (2014), 289,500–289,500 USD (2013)


Remember the GA8 is sold in Australian $'s and 2013 was when AUD was high almost $ to $, prior to GFC and now it is about 30% less.

From memory they started life at around $400,000 Australian not sure, but it was less than 206 price (here in Oz)

[rutan around]

A Squared said:-

Have you got an aircraft certificated in the Normal Category which has a larger cabin than the C172, and can go further and faster with more load than the 172 on less fuel at half the purchase price?

How Embarrassing! I should have checked before posting.You are correct. Jabiru factory built aircraft only come in the LSA category and so in Australia are limited to 600kg gross weight. I suppose it should be of some comfort to know that the same aircraft if built in the experimental category has a 100 kg higher gross wt (and one site said 160 kg more.) The only difference between the two would be the word 'EXPERIMENTAL' written down the side.

So what do we have. As usual nothing is simple in aviation.

1 We don't have a C172 equivalent certified normal category aircraft.

2 If you don't want to build it yourself we do have a factory built LSA 2 seater
J230D with a wider cockpit and a lower fuel burn. Other parameters are much the same as the 172 except fly away price ex Bundaberg. $106,450 Aus or $82,966 USD

3 If you are keen on building you could build in the experimental category a J450 four seater. for around $90,000 AUD ($69,300 USD)
Then for ...... Dah Dah......not half the price, not a quarter the price but about one fifth of the Cessna price you could own a new aircraft that does all the things highlighted above.

[A Squared]

Originally Posted by rutan around

3 If you are keen on building you could build in the experimental category a J450 four seater. for around $90,000 AUD ($69,300 USD)
Then for ...... Dah Dah......not half the price, not a quarter the price but about one fifth of the Cessna price you could own a new aircraft that does all the things highlighted above.

Are you seriously persisting with a price comparison between the 172 manufactured in a factory by paid employees and an airplane you build your self (and thus pay nothing for the labor) which does not meet the regulatory requirements met by the 172, and cannot be used in commercial operations?

Originally Posted by rutan around

1 We don't have a C172 equivalent certified normal category aircraft.

Right. That's kind of my point, You haven’t offered any kind of a reasonable comparison. There is a huge expense resulting from certification with a standard airworthiness certificate. A special airworthiness certificate (LSA and Primary) is much simpler and less complicated. That translates directly to "Less expensive" And the special airworthiness certificates carry limitations which the standard airworthiness certificates do not have. For some potential purchasers, those limitations may not be serous drawbacks. That's well and good, but that doesn't make the comparison valid. The cost of achieving Normal category certification is high, much higher than the cost of LSA or Primary category certification. I'm not saying that is the only reason for 172's high price, but it's part of it. Comparisons with LSA or Primary aircraft, and especially uncertificated aircraft built with amateur labor are completely inane.


Perhaps the reason there aren't direct comparisons is that people have had the idea to build a comparable aircraft for substantially cheaper and after studying the question have discovered that they couldn't.

Off the top of my head, the closest comparison with the 172 of a recently (20 years or so) certificated normal category aircraft is the Cirrus SR20. An imperfect comparison at best, but in approximately the same size/number of seats/ engine power class. Current price of an absolute bare bones base model is $389,000 USD. If the 172 is unjustifiably overpriced, why doesn't Cirrus price the SR20 at 2/3 or even half the price of a new 172?

[5th officer]

All because of greedy unethical lawyers. (eg: suing Cessna, Piper for a pilot error CFIT and blaming it on the aircraft or systems).

Unfortunately Australia wants to follow USA warts and all. This liability thing is out of control here now too.

[5th officer]

Acro, the straw that broke the Camels Back for Cessna was not Pilot Error, it was the failure of the Seat Track on a 1951 170a causing the Pilot to slide rearwards whilst holding onto the control wheel causing a stall after take off. His widow and her legal counsel sued for tens of millions and won, Cessna gave up after that case.

[Acrosport II]

I think the closest replacement available to the C172 is the Maule.

Although, Im not sure if they are certified. Cannot find anywhere that states they are.

So can they only be operated on Private Ops?.

Price is certainly better than the $400,000USD for a new C172.

I certainly prefer the all metal C172, but if I was in the market for a 4 seater for Private Ops, I would certainly look into them.

Maule Air » Maule Aircraft Models

[Acrosport II]

Originally Posted by 5th officer

Acro, the straw that broke the Camels Back for Cessna was not Pilot Error, it was the failure of the Seat Track on a 1951 170a causing the Pilot to slide rearwards whilst holding onto the control wheel causing a stall after take off. His widow and her legal counsel sued for tens of millions and won, Cessna gave up after that case.

This liability issue (with very large payouts for individuals) certainly may be largely to blame for the C172 demise in the current market.

I wouldn't say that a 'seat track' fault on the c170a in 1951 killed Cessna or the C172. 43,000 C172 were built after that along with C170Bs.

I haven't read up on this incident, but perhaps that was the first big lawsuit that all the rest followed. Millions of $ as you stated, would be a considerable blow to Cessna back in the early 1950s.

PS: I'm certainly not saying all C172 deaths were the result of pilot error, or that manufacturers should get away with known potentially fatal design / manufacturing flaws.

No manufacturer is perfect. They should fix the problem immediately. Perhaps that's part of the problem. To admit you have a design fault, you admit liability with that fault, and risk numeral lawsuits.

Some larger aircraft manufacturers may have taken that stance too.

[rutan around]

A Squared wrote

Are you seriously persisting with a price comparison between the 172 manufactured in a factory by paid employees and an airplane you build your self (and thus pay nothing for the labor) which does not meet the regulatory requirements met by the 172, and cannot be used in commercial operations?

If GA is to survive, new, affordable 172 like aircraft are required. Arguably the Jab is as safe or safer in an accident than a 172 so why would a private pilot spend $369,000 USD when the type of flying he wants to do can be bought for $82,966 USD fly away.

If he wants all or more than 172 capability then build a J450 for a kit cost of $ 69,300 USD. It's a pretty complete kit and can be done in about 600 hours of builders time. Say the builder prices his time at $30 USD per hour making labour $18,000. Total cost becomes $ 87,300 ..........a bit more affordable than $369,000 for the 'certified' 172. Not everyone wants to fly their plane commercially and if prices are lower they have no need to.

The difference in cost between a J230D kit and a fly away aircraft is about $14,000 USD so the factory is not too heavy handed with its charges. Certification and insurance must be the killers.

This area of aviation, especially where it involves light aircraft, needs to be put under the microscope and reformed urgently before GA dies.

[onetrack]

The basic failure behind the level of C172 sales is the failure to produce a better product at a lower price, so that more end-users can afford the item.

I do not know of any manufacturers that wouldn't like to sell a lot more of their product. More of their product out in the field means more profits from both production, as well as spare parts sales.

I personally find it hard to believe that certification costs and liability insurance costs are totally restricting any increase in C172 sales.
The major restriction on the sales level of C172's is purely the high purchase cost. If Cessna were seriously interested in increasing the production levels of the C172, they would spend some money on finding ways to lower production costs and purchase cost.

I believe Cessna have no interest in producing more C172's, they are content to sell a minimum number of them at high prices to a range of well-heeled clients to whom cost is no object, and Cessna are happy to keep the status quo and all their current production facilities and methods in place, to ensure good levels of profits from facilities whose setup costs were amortised decades ago.

What is needed is a 21st century disruptor, an "upstart" light aircraft manufacturer with a revolutionary new approach, to shake Cessna to the core, and to get them outside their carefully nurtured comfort zone.