Seagate 4TB Internal SATA HDD $180.99 @ Rakuten

Seagate model STBD4000400, this seems to be the lowest price available for any 4TB internal SATA drive. 5900 RPM and 2 year warranty. This is essentially the same drive in the 4TB FreeAgent GoFlex external but you don't run the risk of voided warranty by removing from the enclosure. So if you just need the internal drive and don't need or want the external enclosure, then this seems to be the cheapest solution for a 4TB drive with full warranty.

http://www.rakuten.com/pr/product...=247557756