I buy 36 bottles of water from Kroger at around $3.50 (plus 7% taxes). Taking one with me on my bike every weekday means they last around two months, at less than $2 per mo.
(Yes, I know it's better for the environment to save plastic. Kroger bottles are not as bad as others, as they feel as thin as a plastic bag, but still I plan to eventually phase them out, but not because of the $)
Yes, but they feel way too heavy/big, and then I have to wash them regularly which is kinda hard to do with a bottle. I know that would be the best long term thing to do though..