Had one in Bangalore, but I couldn't give figures or costs since it was one meter for the whole building - 3 flats - and the landlord just included it in the rent. But I can tell you that the 1000 litre roof tank used to last about 1-2 days for a total of about 7 or 8 people. I read that water there is charged on a sliding scale. I think the first 200 litres a month are free, then most of it is charged at 9 rupees (about 11p) per hectolitre. I think. I do definitely remember that the actual cost of supplying water was stated at 18 rupees (for the same unit of volume) so even at the top end of the scale, water was still subsidised. And on occasions when the supply failed, we paid 200 rupees for a 3,000 litre "half-tanker" of water (into the sump tank, usually supplied by mains, from where it was pumped to the roof tank to supply taps) so that works out at less than 0.001 pence per litre. But the cost was not a factor - rather that there's nothing like shortages to promote water saving!