Why do celebrities get high wages? In the youtube video Why We Look down on Low Wage Earners the author argued: "economics states that wages are determined [...] by the number of people willing and being able to do a given job that others won't do." (video at 1:00). While this explains much of the variance in the wages of different jobs, it does not give in my opinion a good explanation, why celebrities earn high wages.

Take for example actors. There are a lot of people working in this field and there are many more wanting to become an actor or actress. Due to the quoted theory the wages in this field should be low which is not the case for celebrities. The theory does also not explain the variance of the wages inside this field (compare the median hourly earning of actors / actresses with those of celebrities).

My question: How do economics explains the outliers in the wages in form of the high earnings of celebrities? How does popularity exert an influence here? (Do celebrities get much money because they are popular or are they popular because they are rich?) How does economics explains the different wages for a certain kind of job?
If you ask yourself how much a potential employer would have to pay you to convince you to work for him, the answer is probably something like "at least as much as I could earn by doing the same job for another employer". So, provided there are several employers competing to hire workers, you can think of employers as bidding against each other for the best employees. But how much will firms bid? Each employer would be willing to pay up to the difference between its profit if it hired this particular worker and its profit if it took the next best alternative. 

This is why the supply of alternative employees matters. If there are many people capable of doing the same job then a firm's profit if it hires you will be almost the same as the profit if it hire someone else. So why should it 'bid' a lot to hire you? An unskilled factory worker who asks his employer for a significant pay rise will likely be refused because virtually any worker doing the same job would have equivalent productivity.

Celebrities are a different story. Just as factory workers are hired to produce goods for the factory owner, actors are hired to produce movie ticket sales for the studio. But viewed in this light, Tom Hanks or Angelina Jolie are not close substitutes for as yet unknown actors at all. Indeed well-known actors are considerably better at producing ticket sales than unknown talent. Studios are willing to bid a lot to attract top actors because having a star in your cast is worth millions of dollars in extra ticket sales.