14 and some change for a Lifestraw. Unfortunately only one per account but if you have Prime it's free shipping which makes it the cheapest I've seen.
http://slickdeals.net/?sdtid=750985...&pf_rd_i=706814011&pf_rd_p=2001835822
http://slickdeals.net/?sdtid=750985...&pf_rd_i=706814011&pf_rd_p=2001835822