What if I said I have a PSU that can deliver 3kW at a price of ~400 and ~90% efficiency? 
How about 4 of these ($483 total including shipping in the US)?:
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=7580853&CatId=2533
http://www.hardwaresecrets.com/article/XFX-PRO-750-W-Black-Edition-Full-Modular-Power-Supply-Review/1695/13
Up to 92% efficient, fully modular, and top quality (Seasonic KM3 core). Each can power one full rig and be about 90% efficient. Watch out for similarly named older products that aren't as good.