In the 50's, my brothers used to buy model "A's" at a nearby auction for between $40 and 75, then sell them at a small profit. As I grew older I saw those old cars being bought by guys older than me. Guys that got laid for the first time in one of those back seats

Guys with memories that these cars brought back to them in their middle and old age (when they had the bucks to build a hotrod or restore a vintage car their folks used to drive.)
A few years ago those pre 1940's cars were selling for very high prices. Now, they are not bringing half what they brought. Why? Because those guys are rapidly dying off. I don't share their memories with the cars and couldn't care less about owning a pre 1940's car.
We are in the hayday of interest for the post 1950 through early 1970's cars right now. Interest will wane for all but the most sought after cars of that group. Guys who lived their teen years in the 1950's and early 60's have high interest in the 1950-1973 cars now. When their mid life passes into old age, these cars will peak in value just like the model A and model T did.
I expect the same cycle of depreciation, and then, a renewed interest in our TR's and TTA's as a younger generation hits middle age. When you see interest wane a bit on the pre 1980's cars is when interest will peak for our cars.

Its a few years away....
My two cents on this issue.