How would the fuel needed to travel 100 km by Skyhawk compare with fuel needed to cover 100 km by Arnage?
I think a C172 would do about 20MPG (UK/UK). My TB20 does something in that area. So a plane is quite similar to a reasonably decent car.
But the plane would be much faster than any car, due to lack of traffic and lack of speed limits.
Scheduled maintenance is also similar between my TB20 and my 3 litre imported Toyota. A regular service on either is likely to be £500 if you take it to a company.
An old plane will have occassional massive maintenance suprises (of the order of £10k) which you won't get on a car, and if you did you would scrap it. And an equally old car will be scrap already because it fails the emissions, rust around suspension attachments, etc.