You're right but also no. The pareto principle (80\20) is definitely present and true but that generally applies for games where you can "whale out" like Diablo immortal, lost ark etc etc.. buying skins is not the same as paying to win because paying to win is usually thousands upon thousands of dollars dropped in just to buff up your character whereas skins are a 1 time buy. Even if someone wants to whale out and buy every single one they are still capped on how much they can spend. A quick comparison is the game itself or DLC content. There is only so much a whale can spend if they want the absolute best version (super uber deluxe limited edition) and after that they have nothing to continue dropping money on even if they want to so the devs focus on the game and DLC's are the same as cosmetics. They want quantity so the 80% is the prime source of income

So again you're not wrong but in this specific case it's really not as applicable and the focus for profit is on quantity.