Are you opposed to the cloud? You could get an even beefier machine on the spot market for under a buck an hour while you’re using it, then turn it down when you’re not.
I agree with the root comment though that you may want to look at building in a cloud provider using spot instances. You’d have to invest in automation to spin up and tear down machines and manage build artifacts, but it might be more cost effective and operationally simpler than investing in your own hardware.