Surely their price is considerably low, but given the limited locations where people can actually get access to the water, it is not that cheap. Imagine waiting in line with your mobile phone and your cup to get a little sap. You would want a huge water tank to cut down the frequency of fetching water. Good for motorhome users though.

Jesus, how much water do you drink?

I hope you're aware that it's possible to drink too much water and die from it....