Just because it's in a rich area doesn't mean it couldn't be a typical leak.

I have had two properties I rented have a leak in the watering system for the lawn. The first one was spotted right away because of the increase in water usage, by the actual water supplier. Although this was in Vegas so they were pretty quick to identify problems like this. The other was a single family home and I spotted the telltale sign of a leak by a circle of grass growing greener and faster than the rest of the yard. I informed the owners of the likelihood of a leak and they had no idea. The leak was probably there for months if not over a year's time because they had never bothered to check for such things when their elderly mom lived in the house.

Now, imagine a rather large yard of a wealthy family who doesn't watch their water bill, nor care about it, and the watering system develops a leak or three over time.

Houses in rich neighborhoods have pools, and fancy pools with leaks may be cheaper to pay the crazy water charges than to have it repaired right away.

I'm not defending the person, just pointing out that the excessive water usage really isn't that excessive and could be caused by any number of things.