Its really easy to go in circles regarding legroom, but the solutions really are not that simple. It's often the case that you can't pay a bit more for extra legroom.
Let me give you an example, with flights to the Canary Islands. Most of the flights are charter operated, as you may expect. Now of course many of them let you pre-book extra legroom seating, but not all. This is the problem, there is a chance, that no matter how early I check in, I might not get an extra legroom seat, and have the problems already highlighted by others.
As I understand it, Britannia offer extra legroom, but they have recently 'moved the goalposts'. The extra legroom seats are now no longer called extra legroom seats, they are now called 'extra' seats - the difference is in the small print. According to the airline, extra seats provide more legroom by being at an exit row or just more SPACE by being behind a bulkhead, and having no seat in front. This is a significant difference, as someone tall may book an extra seat, only to find that they don't actually get EXTRA legroom.
And before anybody says 'well you get what you pay for' You don't really have the choice to pay more, unless you charter a private jet. I would happily pay more to have extra legroom, but the choice is often just not available at any price
On the upside another charter airline - first choice airlines(Air 2000) have announced that on long haul flights next year, the standard seat pitch will be 33" and premium pitch will be 36". That standard pitch is pretty awesome for a charter. They will get my business.
As regards scheduled airlines, the seat pitch really does vary a great deal which makes many of the cost arguments look just a touch silly (if cost were the main factor, every airline would have the legal minimum seat pitch,but they don't - some economy is 29", yet some is 34"). So clearly cost is NOT the only determining factor.
It is very easy to say tall people should go business class, but that is really quite a silly argument. The difficulty with most of the scheduled premium economy products right now, is that they do not offer what tall people need. Sure, they give extra legroom, and that alone would not be too expensive, but most airlines seem to view this cabin as a kind of half Business class, so you get better meals, and so on, which all make it expensive.
I really wish airlines would just offer some seats with more legroom and nothing else, and that would make life easier for tall people, but at not too great a cost.
As a tall person, I chuckle when I hear airlines say at the start of the safety breifing that 'your safety is our main concern', as this just is not the case, when I and others sit with knees pressed into the seat in front, and could not get into a crash position.
People are getting taller, and yet the minimum seat pitch in the uk has not changed one jot for decades- which is pretty bizarre.
Several good airlines I have found are BMI (on the airbuses), flybe (in the Q400's- which are really spacious inside for a small aircraft), American (but it seems that will change).
Finally, to those in the airline business who don't take legroom seriously, there have been many times in the past when I have had the money to fly to the USA, and have decided not to bother, as I could not get any kind of guarantee of what the seat pitch will be. Try making a booking and you'll soon find that almost without exception, scheduled airline reservation agents and travel agents will not know what the seat pitch is. In addition, in some travel agents, when you ask about extra legroom seats on a charter flight they invariably say "oh can you do that??" or even worse "you can't do that, but the seats are usually ok, you know". Yes, ok for a smurf.