> I can get a Xeon E5-2690V4 with 28 threads and 64GB of RAM for about $150.

If the goal is a lot of RAM and you don’t care about noise, power, or heat then these can be an okay deal.

Don’t underestimate how far CPUs have come, though. That machine will be slower than AMD’s slowest entry-level CPU. Even an AMD 5800X will double its single core performance and even walk away from it on multithreaded tasks despite only having 8 cores. It will use less electricity and be quiet, too. More expensive, but if this is something you plan to leave running 24/7 the electricity costs over a few years might make the power hungry server more expensive over time.