Not sure if I understand the question, but yeah it's all about single thread performance. Around 2017 or so, old server processors had decent single core performance and very good multithreaded performance for workstation workloads compared to the desktop hardware of the day.

Nowadays, old server processors have very poor single threaded performance compared to recent desktop grade hardware, and the much larger amount of cores fails to compensate for that in pretty much all workstation loads. Especially considering that you can get a lot of cores in desktop hardware nowadays too. The relative value of desktop hardware vs server hardware has gone up substantially in the past 5 years or so, since Intel started making server chips focused exclusively on the demands of large scale data centers and AMD started normalizing high core counts in desktop chips.

Because cheap second hand server chips are sourced from data centers, that inherently favor high core counts and only baseline single thread performance, I don't see a future where we have cheap server processors ever being a great choice for a workstation again. Quick-ish single thread server chips do exist (e.g. Epyc 72F3), but I think those are too niche to ever see them for a good deal on eBay.

Having a lot of cores are best used when running virtual machines, handling lots of connections, servicing a large database. The average OS is running 1000 threads at any given time which are all being time sliced to share the same say 40 cores. what you make up in single thread clock speed you lose in time waiting between context switching. The place where single-core performance really excels is Javasript and web browsing. But these machines can process a hell of a lot more data if they’re used properly

Yeah I'm not saying that many cores aren't useful for workstation workloads, but nearly everyone still shouldn't buy these for their primary workstation. If you specifically need to run a lot of VMs or run massively parallel computation, most folks still would probably be better off getting a homelab server to run them instead of running them from your workstation directly.

Agreed personally I find a 5 GHz processor much snappier than a computer with 2.5ghz clock speeds. But that’s also part of DDR4 and other improvements between now and then. It’s not like we’re comparing them to essentially 5/6 generation intel core i7 chips

Thanks, I’m more considering a server for desktop use for some non-standard non technical reasons.

I’m certainly a power user and suspect that additional cores may actually benefit me, but there are some very interesting points about clock speed from you and others.

Hey just because it's harder to rationalize nowadays doesn't make it any less fun to do. Especially if you can get a good deal, go for it!