I got online to get the price for the cheapest bottled water I could find – a six pack of 24 ounce bottles for $2.49 which comes to about 1.7 cents per ounce.
The math: 6 bottles * 24 ounces = 144 ounces. $2.49 / 144 ounces = 1.7292 cents per ounce.
The PiMag Sport Bottle retails for $55 and I went ahead and added in the shipping cost of $8.50 to try to bias it as much against the sport bottle as I could. That brings the price of the sport bottle up to $63.50. The bottle holds 21 ounces and the filter cartridge is good for about 250 refills which comes to 5,250 ounces. They also say that it is good for about 40 gallons which is 5,120 ounces. Again, to bias the numbers as much against the sport bottle as I can, I went with the smaller number – 5,120 ounces. That makes the cost of the bottle about 1.2 cents per ounce.
The math: 40 gallons * 128 ounces per gallon = 5,120 ounces. $63.50 / 5,120 ounces = 1.2402 cents per ounce.
The PiMag sport bottle (at 1.2 cents per ounce) costs less than the equivalent amount of water from regular bottled water (at 1.7 cents per ounce).
But that is just for the first filter cartridge. The replacement cartridges cost $36 for 2 of them. I add in the shipping cost of $8.50 again to make the price $44.50. Two filter cartridges filtering 40 gallons each makes that 10,240 ounces and the cost per ounce is 0.4 cents per ounce. Bottled water cannot compete with that.
The math: 80 gallons * 128 ounces per gallon = 10,240 ounces. $44.50 / 10, 240 ounces = 0.4346 cents per ounce.
Add in the potential health benefits of the filtered water ( alkaline pH, reduced redox potential, no chemicals leached from the bottle) versus the regular bottled water ( acidic pH, higher redox potential, definitely some chemicals leached from the plastic ) and the PiMag Sport Bottle is the clear winner.