Second hand server and workstation equipment is extremely cheap, high quality and powerful. Take a look at z600 and z800 workstations. I'm eyeballing getting a pair of 4.4 ghz dual core CPUs for fast single threaded compile times. They don't require any particular special heatsinks and reach nearly 5ghz with turbo boost. And that's under 600-700 dollars total for those chips. It's a great time for desktop users.
I'm not sure I share your enthusiasm for fast single threaded compile times. Some basic testing on AWS showed benefits jumping from c4.xlarge all the way to 4xlarge (but not 8xlarge) and using appropriate -j parameters. I'm not sure you're IO bound at that point either because compiling into a RAM disk didn't seem to make much difference.
I pay 8! My work that i do is definitely CPU bound but ymmv. These CPUs don't consume any nor energy than is normal for the architecture and die size, which is to say its not the best today's tech has to offer but its no P4.
