It's not, but you're going to pay your fund manager a lot more than your gardener even if both exert similar amounts of effort and skill (I picked fund managers because they're notorious for charging a lot of fees despite their inability to consistently outperform markets).

Or to take another example, suppose you're a lawyer. You'll be able to bill a lot more money to rich clients than you will to poor disenfranchised ones, even though the complexity and challenge of your legal work might be identical. This is partly because people usually assume other people are all utility maximizers; eg within the narrower cohort of criminal defense lawyers, public defenders are generally considered to be inferior lawyers because it is assumed that if they were sufficiently good, they would go into private practice and make more money.