There's a bell curve. Consoles become hyper cheap a year or two after the Next Big Thing that replaces whatever it is comes out, and people start feeling like they can't even give their old and busted machine away. Then some years after that nostalgia starts kicking in and the available supply of non-fucked examples is dwindling, so prices rocket into the stratosphere.

The Wii went through this but the poster child at the moment is the Gamecube. Gamestop was at one point (back when they still sold video game shit and not just Rick and Morty merch and meme stocks) selling complete refurbished Gamecubes for $20 USD. Complete with two controllers, IIRC, all the cables, cleaned, tested, ready to go. Bare Gamecubes are now going for $100-$200 on eBay which is absurd.

...I have like four of the damn things. I have at least two Wiis, possibly three, and a whole extra front loader NES sloshing around I'm not doing anything with above and beyond the one that's hooked up in entertainment center. I keep telling myself this is part of my retirement fund.