I could probably sell my gaming rig (12900K, 64GB of DDR5, 4TB NVME, RTX 3090) for more today than what I built it for about 4 years ago, it's absurd. I won't, of course, because it's still glorious for 4K gaming even today. In retrospect, $5000 very well spent.
After winter, I started playing with various other GPU loads until LLMs and SD became easy enough to use. Now it's my experimentation machine.
It's already paid for itself, so anything I sell it for would be profit, but it is still super nice for running local LLMs that power various projects "for free".
Small Dell Optiplexes are good for desktop computers.