There is a vast middle ground between build it yourself and buy it from Apple.
Honestly, Apple wasn't what I had in mind when I was replying. Personally, I've had to deal with HP z-series workstations compared to various cobbled together machines. Having machines where the series will be in production for a decade, data sheets are readily available, fewer tools needed to open it and install stuff saves so much time and allows less downtime and faster turnaround.