One possibility is that it's not actually being used for anything. A broken pipe could leak that much water, and depending on the local geology it might reach the water table without anyone noticing.

Yeah, but they're being billed $90,000 a year.

I suspect if it was just a broken pipe, the person would be motivated to fix it.

This might be on a 20 million dollar estate though. The home owner probably has never actually seen a single bill, their assistant handles that.

I had a friend who was a "household manager" in Bel Air. Basically a full-time job just handling the administrative work of running a giant house and staff. While part of the job was to be sure money didn't get wildly wasted, I do kinda doubt they'd have known anything was wrong with the water bill.

I could imagine a billionaire wouldn't really notice it, as they'd probably expect it would cost a lot to keep a large lawn lush and green.

It isn't really THAT much. After doing some short math it is about on par with a 10-12 acre farm growing corn (not a big farm at all).

The farm does produce something, however...

Hm... My guess is one of those houses over there with the vineyards, then.

Decorative fountain with no recirc?

I would investigate the country club and the municipality itself, with the expectation that they are using it to water grass.

The user in question was stated by LADWP to be a residential user, ruling out the Bel Air Country Club and the city itself.

Also, a quick search says a golf course might use 1 million gallons per day.