2020 Barrett-Jackson prices?
Complete speculation on my part, but it seems obvious what's changed in demand now from 15, 20, 25 years ago is that back then if you wanted to go faster than most American production cars (i.e. 400HP+) one of the easiest ways to do this was take an old muscle era car and build it up. They were exempt from modern (at the time) emissions regulations that new cars just weren't engineered for yet to get that kind of power. In 1995, the fastest Mustangs (Cobras) and Camaros (Z28s) produced 300HP (sadly no Mopar cars in those years, which is why I had a V8 Dakota). Today the base model V6's of these do that and more, the starter performance V8 models do 450HP+, and the top performance models are upwards of 600, 700, 800HP. On top of that, the cars handle and ride better than ever. So if younger (and rich) buyers love the classic look but want to have the performance and ride of today's muscle cars, it seems logical this is why resto-mod cars are now on the way up.
Just when I finally get enough money to fix up my car (getting older and more job experience = better pay), my 411HP 340 is now pretty standard lol. But still looks cool and you don't see everyday...