I agree a SFH in La Jolla does not pencil out as a rental., but that is more because people who have 20,000 a month to spend on housing are going to buy something not rent. Other than little 550sf cottages by the beach, very few are occupied by renters so in markets like this rent does not have much relevance.
A SFH in La Jolla is a trophy property. These never follow the normal rules because the owners receive value simply from ownership beyond any “rational” economic factor.
I think La Jolla rents are also suppressed by the pickiness of the owners. They worry, correctly, that their home would be used as a big party house.