Why would you want to though? I can understand the retro market because there is software like games that either won’t run very well, or won’t run at all on modern hardware. I’m in the market for a ‘powerful’ machine circa 2003-2005 for that exact reason.

When it comes to machines made in 2015? I’m not sure there’s a lot you can run on those machines that you couldn’t on modern hardware, apart from Windows 11.

I guess you could use them for things like media servers, but it would have to be phenomenally cheap, as in cheaper than cheap modern hardware.

Personally, my rule is a 10 year gap is old, a 20 year gap is retro.

Trade it in to who? Who’s buying PCs that can’t be used? I mean there’s the retro market, but AFAIK they aren’t buying anything after Windows XP.