Even in a (totally unrealistic) scenario where N dollars are &quot;useless&quot; to you, but N+1 get you something of great value, it&#x27;s not true that the (N+1)th dollar has greater marginal utility than any of the other N dollars, because you need all those other dollars to buy the thing. In other words, the previous N dollars weren&#x27;t actually useless: they enabled you to obtain the (N+1)th dollar. Without them, that (N+1)th dollar is just your first dollar.