I had similar problem several months ago. My old Phenom II 1045T@(Gigabyte 790gx/16GB DDR2/Radeon6970) machine started reporting problems with memory. Decided to built a "new one", but not to spend too much money on it. My requirements were: as many cores/threads as possible (development/virtualization), as much RAM as possible (development/virtualization), at least 3.5GHz core frequency (decent compilation times), at least SATA3 capable (I didn't care for NVME), graphic card 4K capable (development).
My first idea was buying some 1st gen Threadripper 1920x 12c/24. It's price was reasonable ~$300 but the price of motherboard twice that much. I gave up. There were also another thing I didn't quite like. All the motherboards, extension cards around were made for "gamers" with "preferred" RGB aesthetics - which I'm not fan of - it's a distractor for me. I'm aware that I can turn it off - but then why spend money on feature I don't like/use. I was looking for boring looking parts. I spent some time researching, looking for hardware dedicated for servers/workstations - mainly Tyan and Supermicro, server processors and so on. I decided on ancient Tyan S7010 (~$100) motherboard, two Xeons
X5690@3.46GHz/6c/12t (each $50), 48GB DDR3 ECC@1333MHz (~$100, yes server memory is cheaper and comes in bigger sticks), Nvidia Quadro K2200 (~100$), and because Tyan S7010 is only SATA2 capable I had to bought additional HBA (LSI 9212-4i - $30). Additionally I bought new PSU Seasonic Focus 750W (~$150) and two brand new SSD disks 256GB for /root and 500GB for /home (both WD, green and blue respectively) (~$100 for both). The only thing I have left from my old machine was chassis - ancient Chieftec (BH-01B-U3-OP) - it's heavy, ugly, without cable management holes or nice tampered glass but with Extended ATX (SSI EEB) support.
I use this machine for programming with 4k@40" TV/monitor with tiling window manager (xmonad) - no need for additional monitors, no additional distractors.
Instead of regular UPS I bought solar inverter
with additional 100Ah accumulator and embedded it in my desk - no fancy UPS management/control but I can work for hours when I'm cut off power.
Final words: I'm not claiming it's the only and the right way to build "new workstation" . It's defnitely not. It's just a funny (and to some extent risky option - no guarantee for most of components) for building decent machine for even more decent money.