I think you are wrong. People dont keep Amiga stuff because they think it is going to be the Antique of the future. They just keep them because they had so much fun using it as a kid.
I still believe that the reason that Amiga's are so expensive on eBay right now is because of the age of the average Amiga user.
Right now the majority have left school/university and are in full time jobs, unmarried and have large disposable incomes, possibly for the first time since they first owned an Amiga, they are also getting to that "nostalgia" part of their life. And so they want to own the Amiga they never could own as a kid.
Give it a year or two... they will be getting married, their wives will insist that they get rid of "all that crap" and the market price for Amiga's will go down.