There is actually a thriving vintage PC community, and the vintage PC community is quite different from vintage Mac land for one big reason: what was "good" at the time is not necessarily what you want in a vintage system.
In vintage Mac land, the most desirable systems are basically the best/last systems of a particular era, along with a few that had iconic designs (but, of course, the two sometimes combine - e.g. the TiBooks are the last OS 9 PowerBooks and an iconic hardware design). In vintage PC land, the eras are far less clear-cut, so the "best" Windows 98 machine may be something "mediocre" from 2006 that still supported Windows 98, whereas the nice hardware from 2006 was XP-only. But the "mediocre" hardware from 2006 is still better than the "nice" hardware from 2002. To pick an example, the GeForce 5xxx cards are highly-prized in vintage PC land because... I'm not sure, either something about earlier DirectX version support or something about Windows 98... but back in the day, the 5xxx cards were NVIDIA's first huge flop and everybody was running ATI Radeons 9700/9800. And, to go back to your Celerons, it is certainly possible that a newer-model Celeron on an older socket/chipset is a better retro system than something nicer from the same year - I have actually seen a lot of retro PC enthusiasm for AMD Socket 754, for example, which was all but forgotten in the mid-2000s.
And similarly, because there is so much more forward compatibilityn than in Macland, when you are e-wasting a 2000 machine in 2010, you (foolishly) are thinking "this is a mediocre XP machine that can't run Vista" instead of "this would actually make a great retro Windows 98 machine" because, well, you stopped running Windows 98 on it in late 2000.
Interestingly, there seems to be very little retro interest for Windows 2000, which makes sense because I think vintage PC land, perhaps more than vintage Mac land, is driven by vintage games that won't run on newer software (and in the case of DOS games with CPU timing issues, newer hardware). And if you want to break out games by era, you have the "DOS-as-far-away-from-Windows-as-possible" era, the Windows 9x era culminating in 98SE, and the "oh god we game developers actually have to support this NT thing now?!" early XP era. Then most things from the late XP era are fairly likely to run just fine on a modern Windows machine, especially if they've been re-released on a Steam-like marketplace without older-fashioned copy protection schemes broken on modern Windows.
And for the record, I was shocked to see someone advertising on Facebook Marketplace recently my first DOS/Windows machine from 1995 for like, $150CAD or something like that that was real money. This is a Mac forum so I won't get into a big list of reasons why, with the benefit of hindsight, it was a total piece of trash and there are (or at least, were) a lot of non-trashy 486 machines out there if you want a vintage DOS machine, but somehow, someone bought it. This one didn't even have a RAM upgrade - for me at least, this machine needed its first RAM upgrade in its first three months so it could run Office 4.2 (yes, the famous Office 4.2 with the dreadful reputation in Macland). Also came with the 14" CRT they bundled it with at the time, which again, was one of the greatest pieces of garbage CRTs of its era (640x480 at 60Hz, 800x600 at 56Hz, 1024x768 interlaced 85Hz makes for one hell of a great experience). It's weird - I paid barely more than that for my 5,1 Mac Pro with 64 gigs of Apple RAM - but I assume it must have sold for close to the asking price.
