One single billion at any one time is more than any one person should have. There really should just be a cap. Like, 999,999,999 is the highest your bank account can get, anything after that just flows into public programs.
The game Zelda: A link to the past had a max capacity of 999 rupees (money). If you picked up more, nothing happened. That’s how life should be.
Well, inflation has made that more than 10 million, but yes I agree there is a number that says “I own a huge mansion, 10 cars, a yacht, and I eat caviar every meal.” That number is significantly less than a billion without having to work a day more.