The whole point is that used business machines are way cheaper... like 50/60 each maybe 100-120 max.

Ah, used changes the game. I optimized for compilation speed (in the tiny box category), so a used Dell would not have helped me.

Companies sell these off after just a few years as warranty goes out. You can pick up 2019/2020 machines on ebay. Fast enough for most things.

There's no such thing as "fast enough" for Rust compilation. I'm putting the AMD CPU, 96 GB RAM, and a fast NVMe all to good use and still have time for a sword fight..

It's likely 5x as expensive as a used 7020: https://www.ebay.com/itm/135220765637

OTOH it's of course new and modern vs used and aging.