I am sure flying is no more expensive than it was say 30 years ago.
Fuel, adjusted for inflation, costs no more, and I bet you that the same goes for general operating costs.
The circumstances have of course changed massively. These days most people in GA are looked at as anoraks (and it isn't far wrong) so I guess that while "I am a private pilot" might have been a good line at a 1970s party, it is less advisable today (if you are trying to pull)
The machinery has hardly changed. I have a photo I took of my local airport from 1979. The only change is the perimeter fence. The planes are exactly the same. Back then many must have been nearly new; now they are decrepit old heaps of junk. This suggests there was a lot more money around back then - how many people do you see buying new Cessnas or Pipers (or anything else new) today?
There are significant regulatory dangers to "utility" flying i.e. anything under IFR. There is pressure from airlines who would universally like to totally kill off GA. Not necessarily kill it off directly, but kill it off through equipment requirements which cannot be met in a GA plane. I don't think this will happen, because of ICAO obligations and pressure from pilots.
But I think purely-VFR "sports" flying, without a purpose, outside CAS, has a very secure future, and will be served by a vast choice of Rotax engined plastic buckets.
As for "halcyon days", those ended about 1946.