Same for ebay, too. Sometimes these old keyboards that didn't sell billions and billions of units like IBM are pretty hard to come by, and you're SOL. It's one of the reasons they often go for more than they're really worth, as opposed to some keyboards like the AT101 and the Model M, of which there are so many units, they sell for under what they're worth, IMO.
Of course none of that makes a lot of sense, but like, I mean, you get more keyboard for your $50 with an AT101 or Model M than you get for your $50 in other vintage keyboards you're looking for specifically.
What I do sometimes i just search for "keyboard" on ebay, and sort by used and hope to find a gem. It's how I got some pretty cool stuff for like $10, though I will say I never buy random Alps boards because the switches can go to **** quickly.