When people ask what computer they should buy I always tell them to get any old office computer from ebay and use the rest of the money to buy a really nice monitor, and a really nice keyboard and mouse, as these are the bits you use! For most tasks that are undertaken on a computer any processor from the last 10 years coupled with 16GB of ram is more than sufficient.
I have a ThinkPad T420 that is sufficient for most tasks that don't involve HEVC acceleration. It's got a mobile Sandy Bridge i7, booting off of a SATA SSD.
The only thing that really needed an upgrade was the display. I ditched the crappy 1366x768 TN for a 1440p IPS and an LVDS-eDP conversion board. Looks fantastic. Runs great.
If you buy a really nice monitor, which for me starts at 6K 32” - the eBay computer will no longer drive it. What I find insane is how long companies issued 19” 1080 screens to their employees. I don’t think that was a well calculated choice given that a couple of hundred more over 5 years would have surely improved productivity by a little bit for their 50k year employees. It felt almost done out of spite to keep people in their place