Yeah.. CHEAP PCs... sure. The thing is though, even very high end Macs are conservatively clocked, and their range of GPUs is archaic unless you go for a Quadro or Fire option. If you just want a normal GPU, their terrible. RAM speeds in Macs are also rather pedestrian, as is PCIE management. Too expensive, and too slow. Of course that's just my opinion. If you're more interested in being cool than being fast, sure, knock yourself out. Thing is though, I don't see how buying a machine identical to everyone else's is cool.
Same processors etc is one thing, but motherboards in Macs are mainly crappy Foxconn derived stuff. Nothing can touch a decent high end PC board for reliability, and expandability... nothing. A high end Asus Rampage board is a thing of beauty... so well built, and so feature rich is beggars belief.
There are loads of suppliers that will offer superb after sales service for PCs. Scan Systems spring to mind immediately. You're suggesting that no one will repair a PC once it's out of warranty, which is patently nonsense