I just built a Xeon X3470, Asus P7F7-E motherboard, 8GB DDR3 RAM, and GTX960 for $350. I had the drives, PSU and case, but that would still only cost maybe another $200.00. Samsung 830 SSD, assorted other HDDs, Strider 750 Gold PSU, Antec NSK 4462 case, and a Hyper 212 Evo.
So - total was $550 - all parts available on eBay.