San Francisco is the most expensive ($148k); second is New York City ($87k). Lots of places in the $45k to $65k range.
Fascinating article about how New York City gets its water and why it tastes good.
Water usage has actually decreased more than 30 percent since the 1980s. Modern toilets, faucets and showerheads use less water. The city has also hunted down and fixed leaks in water mains.