Salaries are related to the initial Staff level.Once they drop, the salary stays the same - that's the incentive to not just keep the staff member for a really long time.
Salaries for different coaches who were originally "10" are not the same.And this would naturally lead people to question whether a 10 coach with a higher salary was better than a 10 coach with a lower salary. But the BB's have said that there is no difference. One advantage of not having a fixed salary is that they can use the salary to regulate the number of "10" coaches in the game.