At that point, the earnings per million views cease to be centrally important because the creator has a brand they can capitalize on: many big YouTubers have patreons, sell t-shirts and other merchandise, and occasionally even use their fame to start kickstarters for pet projects, etc. Further potential avenues for profit include the occasional speaking engagement, paid promotions/shoutouts, etc. (Though the latter is rare among the most subscribed YouTubers, because they're afraid of compromising their brand.)