On the other hand, these are running on some big cluster with a whole bunch of CPUs, so I wonder if you’d still get 3m per build on something like a laptop?
Any individual build they're referencing there runs on a single vm (the cluster referenced there is the k8s cluster being built up and torn down on that vm to run e2e tests on). It looks like at the time they were using GCP standard-8 instances, which are 4 core/8 thread w/30GB of ram. It's hard to say exactly what the current build time is, as it looks like they do some build caching now; on my desktop a fully clean build of current kubernetes master (3.2 million loc) for linux/amd64 takes just under 2 minutes.
