I bought my Aeronca Sedan in 1988 for $10000. At that time I was driving 70's vintage cars. Aeronca Sedans have increased in value 2 1/2 to 3 times in value since then. The 70's cars have increased in value more, some of them much more.

It seems that one thing you don't see is an old plane that is more valuable than an equivalent new one.