Whale
Also said as High spender, Big spender, VIP, Dolphins and minnows
Trade slang for the small number of players who spend far more than anyone else. It comes from casinos, where it means a high roller.
Question the word. It is a way of not thinking about who these people are: some are rich, some are lonely, some have a gambling problem, and some are children using a parent's card. If your income depends on them, you have a duty to find out which, and a spending limit is one way to act on it. How concentrated spending is differs by game, and most published figures come from vendors, so do not borrow one: measure your own.
Say it
“Stop calling them whales in our dashboards: call them top spenders. Add a monthly spending cap, on by default, and a human who contacts anyone spending over $500 in a month to ask if they are fine.”
Not to be confused with superfan
A superfan loves your game. A whale spends a lot on it. They can be the same person, but the word only measures the second.