Well, as the interests that yield any given amount of money vary with time, location, and even the identity, personality, or abilities of the person with a give

Well, as the interests that yield any given amount of money vary with time, location, and even the identity, personality, or abilities of the person with a given interest, the implied conclusion that one should simply choose a "higher-yielding" interest, and that failure to do so is a personal matter that absolves any interest/pay relationship of unfairness, seems... incorrect. Maybe axiom was the wrong word. The intent was to convey that the original quote meant to present "and that some interests yield far more money than others" as an "obvious", self-evident notion immune to decomposition or factoring. And it isn't.