Best Buy via eBay offers the Tile Mate Bluetooth Tracker 4-Pack for $49.99 with free shipping. (Amazon and Tile charge the same.) That's tied with our mention from a week ago, $12.50 each, a low by $18, and the best per-unit price we've seen. (Most major retailers charge $80 or more for this quantity.) It attaches to something that you don't want to lose, such as keys or a backpack, and can be tracked from Tile's iOS and Android apps.