I've been replacing older systems with last gen hardware off ebay. I'm typing this on a Thinkpad T14 i5-1250p 512GB 32GB WWAN I picked up last week for $370 all in.
Since this mess started, I've bought dozens of unused and like-new systems for clients. All with modern hardware - in the $250-$600 range.
Craigslist still exists, too. Found a really nice ~10 year old HP workstation for $100 and crammed as much DDR3 ECC RAM (still cheap) and the bets Ivy Bridge CPUs (cheap) I could find into it, and it shreds.