It is the auction mentality, competition, plus the thought that it is a bit like a "barn find"-- any one who has bought a fixer upper anything knows--
My house was a project 30 years ago, and now it is a bigger project. ;-)
OTOH, if you are willing to put a great deal of time and effort, or are very lucky-- keep looking at places like good will--
A student friend found two Hassies, with lenses, at one in Cincinnati for $50.
People also back out of their auctions as well, and they accept returns often if you just call them.
They had a Nikon FM2 with a stuck shutter, I called them and told them the battery was probably dead, and to reset it by setting it to the manual shutter speed-- worked and they got a better price for it-- it is a charity.
Regards, John