Cheapest water purification tablets per tablet

1. 1
   Potable Aqua Water Purificatio, Portable and Effective, 50ct$0.11 per tablet 100 Tablets $11.01
2. 2
   Aquatabs 49mg Water Purification Tablets, Backpacking$0.36 per tablet 50 Tablets $17.99
3. 3
   Aquatabs Water Purification Tablets, 397mg 100 Pack$0.40 per tablet 100 Tablets $39.99

Prices as of Nov 13, 5:33 AM UTC