It's absolutely overpriced on eBay.
I've had amazing luck with Facebook marketplace and Craigslist, though not just waiting for listings. I make posts saying I'm buying old computers, and kinda generally sketch out what I'm looking for - nothing specific but things like 'Need PC from late 90s for project' or something.
You will, eventually, get a couple of nibbles here and there and sometimes land a legitimate deal but it does require a lot of time and patience that it didn't require a few years ago when you could just literally go get all the retro computer e-waste you could stuff in your car for $0.
You you happen to live near a large urban area? I haven't been able to find much around there.
Yeah, I do. I can imagine if you didn't happen to be close to a major metro area you probably would have a heck of a time finding anything.
As it is, the pickings have gotten slim because the garage sale/estate sale scalpers have figured out that old computers sell on eBay for stupid prices, and they're snatched up by the "pros" pretty fast.
I'm looking daily on Facebook Marketplace and Craigslist, but it's insane how things go fast on there! I'm on a few Facebook groups as well. I feel like I'd have to monitor them 24/7. And when you do find interesting stuff, it's not within range. It's like there's a big invisible and competitive market for old computers.
A lot of the issue is there's not really as much old hardware out there as you might think.
Nobody kept their old computers safe once they upgraded, they got sold cheap or trashed or whatever. There was never really a time when old computer hardware had a lot of retained value over maybe a year or two from its release because stuff moved so fast that things got obsoleted rapidly and the value hit essentially zero within a reasonably short time.
And a LOT of what's out there doesn't work because, well, working for 20 or 30 or 40 years was never part of any design decision for any computer - if you got 5 years out of it was a good run.
Worse, there are entire generations of hardware that flat-out fail - the capacitor plague, for example.
Basically, nobody 35 years ago thought there would be a time with an IBM 5150 would be valuable, so very few people bothered to keep them when they upgraded.
Also check out shopgoodwill.com - it takes a while to find good searches (for this I like "vintage computer") but there are often systems and parts on there. Right now I don't see a 486 (though there often is) but I do see an Aptiva, XT clone, a couple of 386 laptops etc. You can also sometimes find parts, like if you do a search for "graphics card", though you'll have to go through the results yourself to find a good VLB card. Another good search for components is to go to the Computer Components category and search for "vintage".
Prices are all over the place, just depends if someone ends up bidding against you. Even when that happens I don't mind quite as much on there though since I figure at least the money is going to charity.
Just a couple years ago, I could have pointed you in the direction of some really good recyclers that could get you enough parts to build a fun 486 or Socket 5/7-style machine, if you weren't too picky about what you got. Unfortunately now the supply has either dried up or the recyclers think their extreme budget clone parts are solid gold. The only time I find parts now is when I stumble across them at thrift stores or estate sales.
I like buying "broken or for parts" for cheap on eBay, and just gambling essentially. Lately I've been eyeballing stuff from Japan on Buyee, but that can also get expensive with shipping.
Some metro areas have businesses that sell technology from our past lives, like WeirdStuff in Sunnyvale (which, uh, closed five years ago ... oops) or RE•PC in Seattle.
Also this is one of my excuses to hoard things.
All Electronics in LA will ship, but they rarely have computer parts.
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