Opportunity cost : your ressources are sometimes better employed elsewhere

In order to gain and to hold the esteem of men it is not sufficient merely to possess wealth or power. The wealth or power must be put in evidence, for esteem is awarded only on evidence. And not only does the evidence of wealth serve to impress one's importance on others and to keep their sense of importance alive and alert but it is scarcely less use in building up and preserving one's self-complacency.… Abstention from labor is the conventional evidence of wealth and is therefore the conventional mark of social standing; and this insistence on the meritoriousness of wealth leads to a more strenuous insistence on leisure.[...] According to well-established laws of human nature, prescription presently seizes upon this conventional evidence of wealth and fixes it in men's habits of thoughts as something that is itself substantially meritorious and ennobling.

It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own self-interest. We address ourselves not to their humanity but to their self-love, and never talk to them of our own necessities, but of their advantages.