Beach Camera via Rakuten Shopping offers the Western Digital My Cloud 4TB NAS, model no. WDBCTL0040HWT-NESN, for $179 with free shipping. Outside the price below, that's the lowest total price we could find by $6. (For further comparison, we saw a refurbished unit for $19 less last week.) It features USB 3.0, WD SmartWare Pro backup software, and password protection.

A close price: B&H Photo-Video and Amazon has it for a buck more.