Nah, you can’t earn a billion dollars. Dig the hourly rate for someone working 50 years to hit a billion. It’s just not possible. Nobody actually does that much good or delivers that much value. They just happen to capture or steal it somehow, combination of guile and right-place-right-time. If they “earn” it at all.

It’s an artifact of our system that creates a few kinda capitalist-aristocrats, with about the same (poor) level of justification for the power they wield as feudalism had for dukes and kings and shit. Complete with it often having a hereditary element.

[EDIT] Nb I'm not proposing an alternative, and I'm not sure how we might eliminate that wart on our system without doing more harm than good. But once you break a few tens-of-millions net worth, the rules of our economic system start doing some weird and probably not all that great things, "risk" becomes mostly pretend, and you can "earn" more than most do in a lifetime just being a middleman on access to your capital, and not necessarily a very good one. That reaching these levels isn't super connected to competence or expertise at acting as that sort of middleman—doubly so if it's inherited—makes it all rather inefficient and unfortunate and certainly unfair and even corrosive to democracy (since money converts so well into power), but, it's the system we've got and no, I don't have a better suggestion. But it's surely comparably unjust and evil to rule-by-divine-right and all that, which we're all used to dismissing as plainly silly and bad. A difference of small degree.