“How do they know the patron was wealthy?”
Quite true; after reading the story and thinking about a “$133 bill for lunch” that’s either a lot of people, or an outrageously expensive restaurant, even for California. The tip could be a protest at being gouged by the bill.
Lunch entrees there average about $12. So it was either a large party or they were drinking heavily.
Rich, arrogant, and unable to read a menu is no way to go through life.