It may cost slightly less in direct costs, maintenance wise to operate the aircraft however any saving will be quickly eaten up by the purchase price of a new airframe. Your Baron example is good as a brand new Baron would set you back $1.5million where as you could make your $150,000 dollar machine quite good for a total spend of $500,000 (zero time most componants, re-paint, refurbish and upgrade the avionics), you have saved a million in finance. After a few years or 2000hours of being looked after properly you should get at least $200,000 where as the brand new machine would probably be worth under a million.
The direct operating cost difference between the two machines would be negligible.
Things like corrosion depend on the aircraft and its history and location, a good pre-purchase will sort that out. I have seen 40 year old aircraft with no corrosion problems and brand new aircraft only a few years out of the factory with major problems due to manufacturing issues.
The main difference between a light aircraft and a car is that a new car has little in common with one from 30-40 years ago. Engines, body and chassis are built with different techniques and materials. A new Baron or Seneca is essentially built the same way as the old, from the same stuff and has the same engine with maybe an electronic control unit attached and some fancy new avionics and interior.
Last edited by 43Inches; 9th Jan 2011 at 09:29.