This comment is demonstrably untrue. You likely understand the concept of marginal utility even if you haven’t heard it. It’s why someone who earns a comfortable living does not even think twice about getting a PT job washing dishes. The extra few hundred dollars a week is NOT worth the effort in a way that it might be for someone who is not earning a comfortable living.

Opportunity cost is another concept I am certain you’ve heard of. Ever turn down a job offer even though it paid better than your current job? There are tons of factors that go into that kind of decision. I remember heading into the financial crisis reading that people in the oil patch in North Dakota were pulling down $100k+ for mopping floors. I was earning $30k as a jr. copywriter. I didn’t want to move to North Dakota to mop floors, even for $100k — not because the money wasn’t good, but because I realized I would be giving up a promising start to a long term career for a shaky chance to earn more in the short term. I chose to earn less money then.

I earn a comfortable living today, and I have turned down plenty of “extra” work because I value time with my family or leisure time, or time to pursue hobbies, over earning that next, marginally useful dollar.