reply to Maniak
Re: Water usage and bill.. You already found your stats, it seems: 10k per month in a 4 person household.
I find stats saying 2500 to 3000 per month per person.
It would coincide with your numbers (4x 2500 = 10,000).
As for how much, well, it depends doesn't it? You just said that different co-ops charge differently.
As for me, where I live, I don't know how much it costs. There isn't a meter, so we pay a tax based on the municipal value of our house.