What is the correct answer to the “billionaires shouldn’t exist” argument?

Not sure if this falls under politics or not but it seems, like everything else, that there is no middle ground on this issue. Which probably falls in line with there being no middle class.

You’ve got one group shouting “no one needs that much money, why can’t they cure world hunger” and another shouting “that’s part of capitalism they earned it, if you work hard enough you can be a billionaire too!”