As a homeschooler, we have what we call the Madonna principle. Madonna's product is essentially worthless, and the product of say an ER nurse is absolutely vital. However, the market is such that Madonna can sell her product to several million people a year, and the ER nurse, while more valuable, can only sell her product to several hundred to a couple thousand people a year. It's not that we value Madonna more, it's that her market is such that even at next to no value, it makes her gazillions.
You know, that's an interesting perspective and one I hadn't considered. Sheer size of the market does make a difference.
I have always told people who bitch about sports stars making millions that they should not at all be upset. After all there are many millions of people who for instance love to watch baseball, and very very few people who can throw a 95 MPH split finger fast ball, and even fewer who can hit one. The demand for those individuals is very high, while the supply is very low, therefore the salaries are in fact proportionate. It's perfectly logical that they should make lots of money.
But thinking about Madonna, (ugh) I have to revisit that stock answer. Like baseball, there are absolutely many millions of people who enjoy watching half naked tramps sing and dance. But unlike baseball, there is no shortage of tramps willing to sing and dance while removing their cloths. Every town has at least one titty bar where women every bit as "good looking" or better than Madonna do it for a few bucks stuffed in their G-strings, and lots of other bars where they do it for a few cheap beers.
I guess there is no logical reason why Madonna should makes millions. ;~))