Regardless of what industry you are in, the closer you are to money, the more honestly you will be paid. This is why in many companies some of the best paid people (sometimes more than executives) are in sales. It is quite difficult to tell an employee that you can only manage a small raise if they can say "I brought in $15 million in business this year." If they have no discernible way to determine what they have earned for the company, they can be had for a song.