Amazon has the Toshiba 5TB 3.5-inch internal hard drive (PH3500U-1I72) on sale for $159.99. It ships free with Super Saver Shipping.
Toshiba 5TB SATA 6Gb/s 7200rpm, 128MB Cache, 3.5-Inch Internal Hard Drive (PH3500U-1I72)
Edit: It's currently out of stock but you can order now and Amazon will ship it when they get more.