1:20:80 Brackets

In a free-to-play mobile game 80% of players will never pay a single cent. Any money from them is from ex. ads.

20% of players will pay you at least one time.

1% of total players pay you repeatedly; these are also known as the "whales."

From a book on the "Octalysis Framework," which analyzed free to play games based on their analytics and design.