Buy.com via eBay offers the Seagate 4TB Backup Plus USB 3.0 External Hard Drive, model no. STCA4000100, for $139.99. With free shipping, that's $0.03/GB and tied with our expired mention from earlier this week as the lowest total price we've seen for a 4TB USB 3.0 external hard drive. (It's also a current price low by $9.)