Western Digital Store offers its factory-refurbished Western Digital My Book 4TB Portable USB 3.0 External Hard Drive for Mac, model no. RWDBYCC0040HBK-NESN, for $89.99 with free shipping. That's tied with our March mention as the lowest total price we've seen. (It's also $39 below what you'd pay for a new one now.) It features password protection and hardware encryption. A 30-day Western Digital warranty applies.