Unfortunately people watch these doppy US car shows, with inflated (US$) prices, and think they can demand the same here. Or they spend money rebuilding or glossing up cars and think a buyer is prepared to pay for their folley. There is a Red 87 Calloway for $60K, it's been for sale for years I think, someone who wants that type of car may buy, I certainly would not fork out 60 large for any C4. And I suppose whilst ever he does not need the cash, he will leave it up for sale and wait.
People also think they can buy an old bomb, tidy it up and make a killing, those same US shows, are the cause of that inane thinking.