Compiling rust code is slow and cpu bound. I have a fast cpu in part to improve compile times while I’m programming.
I did not change mine for 6 years, but looking at some benchmarks, it looks like compilation times would not get more than a few percents faster per generation. I expect to get maybe 20% faster with a recent CPU in the same price range.
Until 2005 I was updating the CPU every 2-3 years, then every 5 years, and when I'll get the next one I plan to keep it 10 years easy.
This is the biggest difference I see today. In the previous generation it was a huge boost in everything just becauase the old CPU was really old. I also keep CPUs 5 years or more.