It is about value created. A programmer who can find a way to extract $1 per year, from a million users, is worth $1m. But doctors are constrained by their personal 1-1 relationships: no doctor can handle a million patients.
It is about supply and demand in the labor market, full stop. People aren't paid based on the value they create. They are paid based on how hard it is to find other people who can do the same thing.
People are paid based on both the value they create, and how hard it is to hire them.
If someone being hired will provide $10 of value for the company, then that is the ceiling for their wages. On the other side, the floor for their wages is the lowest price sometime will accept to provide that value to the company.
