shcifang via eBay offers the TOCCs 2,600mAh Power Bank Key Chain in six colors for $4.67 with free shipping. That's the lowest total price we could find by a buck and the best per-unit price we've seen. This key chain adds up to 10 hours of usable power.
Dollar stores lure us in with their rock-bottom prices, but not everything is a bargain. We suggest you steer clear of these items.