1TB SSDs are consumer drives nowadays, if you want to spend money you can get 2+ TB already, same deal for CPUs, you can get 128GB/8core with consumer CPUs and consumer motherboards (asus x99 deluxe, intel 5960x, corsair lxp 128 kit), the higher end would be xeons or dual xeons where you can get a lot more cores/ram for a lot more $$$.
I agree that you can hit a point of diminishing returns, but it also depends on what you work on, being able to spin up a few VMs to do long-running tests on without impacting your main development environment can pay for itself very quickly, IMHO if you hire somebody good at current rates and expect them to stick around for 4 years, 10k in hardware is still only a couple % of what you are going to pay them over that time, which is immaterial in the grand scheme of things, profitable or not.