1st of all this isn't a regular, run of the mill car. so you need to compare apples to apples. also, there's a reason auction cars bring so much money, they are unique examples of specific models that are "generally" held to higher standards than something joe dickhead on c'list is peddling.
saying that if regular car guys bid on it, that the numbers wouldn't be there is a BS argument. people will always want something different, special and unique-- and if that is what is attractive to them they will pay for it. for example see cheap burbon vs expensive limited run burbon.
the idea of return on investment isn't part of the discussion. yes, some people buy as an investment but many people buy because that's what they want, and nothing more.
i would agree that a low mileage 74 duster would be considered over priced at 40K, but if it's absolutely perfect and that's what somebody wants, then that's the going rate. would i pay that? no, because i don't like 74 dusters. that doesn't mean it's not worth it.
some prices have come down, but upper tier cars remain firmly priced. there has been some adjustment for what i personally thought were inflated prices, but it's not like stuff is coming down to 1994 1/2 prices hombre.