I believe that's because the selling rates are higher for Coke because it's yummy and people don't buy water as much as Coke because water tastes like... well, water.
So if the selling rates are higher, they don't have to put that much effort into the pricing.
Everything labeled simply "Purified drinking water" came out of a tap and was filtered before bottling. Something we do in our home for the price of a mounted tap filter which runs about ten dollars every 200 gallons (estimated lifespan and cost of replacement filters) This does not factor in our $30 to $50 monthly water bill which is noticeably higher during the summer as we have 7 to 9 adult German Shepherds at any given time sharing 4 to 5 kiddie swimming pools and a 5 gallon water bucket per dog in each 20' X 20' covered dog pen. Furthermore, it is worth mentioning that we dump and refill water buckets daily and pools weekly thus driving up our monthly bill. And before everyone jumps on the "PETA misguided sympathy train", only one our pens is at full capacity temporarily, housing 3 of our stud dogs until after Emma's litter, due in 7 days, leaves for their new homes at 8 weeks of age.
Ya, but where I live in Canada, we only have to pay a monthly fee for water, and we get as much as we want, so it's not very expensive. It's different everywhere.
Ya, but many sub-divisions, apartment complexes, municipalities, etc. in America are the same with no water meters installed. So... the rest of the free world does not have the market cornered on this concept. Sorry to burst your Maple flavored bubble. ;)
So if the selling rates are higher, they don't have to put that much effort into the pricing.