This doesn't surprise me much. Most of the cost of these things is the cost of packaging and trucking them around - the cost of the sugar syrup in Coke isn't adding much cost versus the sparkling water. The soda maker might have a more efficient distribution network that allows a lower cost per unit. That, and the customer who's buying sparkling water (instead of buying soda, or just plain bottled tap water) probably is willing to pay more.