The problem with opportunity cost is that opportunity cost is divided among many, many things.

The more cashless our society becomes, the more our moral compass slips.

What kind of people would be able to rationalize better than other people? Better storytellers, right? Creative people, right? Because if you're creative, you find more ways to cheat and still yourself a story about why this is okay.

A very simple bad decision is to get into debt. And that is very expensive.

People are willing to work free, and they are willing to work for a reasonable wage; but offer them just a small payment and they will walk away.

If I gave you now, $10 as a gift, how happy would you be? Would you be happy, is the marginal $10, the best use of $10 you can use? Of course not. If I have you a CD, you know exactly what you are getting and you will have a value for it. So, money has lots of problems with it.

To summarize, using money to motivate people can be a double-edged sword. For tasks that require cognitive ability, low to moderate performance-based incentives can help. But when the incentive level is very high, it can command too much attention and thereby distract the person’s mind with thoughts about the reward. This can create stress and ultimately reduce the level of performance.