The Good Blokes via eBay offers the PNY 16GB Attache USB 2.0 Flash Drive 4-Pack in Black, model no. P-FD16GATT03-GE, for $15.99 with free shipping. That's $4 per drive, the lowest total price we could find for this quantity by $12, and the best per unit price we've seen without credit offers. (We saw them with a $5 store credit for $8 each in December.)

Also available is the PNY 16GB Mini Attache USB 2.0 Flash Drive 4-Pack in Black, model no. P-FD16G/MINI-EFS2, for $15.99 with free shipping. That's $11 under the lowest total price we could find for just one of these drives elsewhere.