newegg offers the Netgear ReadyNAS Ultra 4-Bay Gigabit Ethernet Network Attached Storage Enclosure, model no. RNDU4000-100NAS, for $529.99. Coupon code "NET829US" cuts it to $499.99. With free shipping, that's the lowest total price we could find by $19, outside the price below. This enclosure features an Intel Atom 1.66GHz single-core processor, Gigabit Ethernet, three USB 2.0 ports, one USB 3.0 port, multiple volume support for RAID 0, 1, and 5, TiVo compatibility, and more. A 3-year warranty applies. Note that disks are not included. Deal ends August 31.

A close price: NextWarehouse charges $503.30 with free shipping.