One of my uncles recently told me that one of his daughters had discovered that a newly-hired man at her workplace (a state institution) was being paid an "extraordinary" amount more than she or other women at the same level. My cousin initially assumed that this man must have some extra credentials or experience, but she did some quiet investigating and found that he did not.
My cousin talked to her boss to ask him why the new guy was being paid so much more than women who were his equals in experience and credentials. She assumed there was a good reason, but wanted to know what it was. It turned out there was no good reason, and my cousin and the other women were given "extraordinary" raises so that they were making the same (or more) than the new guy.
My uncle was shocked that his daughter had questioned her boss, but was impressed with her for getting such a big raise. He said to me "What I can't figure out is why she and the others got such a large raise when all she did was ask why this guy was being paid more." I told him that I thought my cousin and the other women could have sued and won, and that would have cost the state more and gotten the supervisors in trouble. In the end, the women probably would have gotten the big raises anyway. I said "You can't pay men more than women for no reason." Well, OK, you can, but I didn't feel like saying that.
This really surprised my uncle. He said he assumed that the salary you were paid was the salary you "deserved". I don't really know what he means by "deserved", and he couldn't explain it. He said it wouldn't have occurred to him to question why a man was being paid more than some women ("girls").
In many jobs, including some academic jobs, you get the salary that someone else thinks you deserve, and they may think someone else deserves more, but not for any particular reason that makes sense.
The mechanism for determining academic salaries varies widely from institution to institution. For state universities, the mechanism varies from state to state, and may also vary within a state if there is more than one university system. Even in systems that have salary ranges for specific ranks, there are ways that these ranges can be adjusted.
On two occasions I have acquired the salary data for faculty in my department. All of the highest paid faculty are men, but these are all men who have been or are administrators and/or are the department superstar. There is one outlier that makes my gnash my teeth when I think about it.
If you consider my individual salary compared to my department colleagues, there are some senior men who make less than I do (owing to their long-term lack of productivity), and there are coeval men who make more than I do (owing to nothing obvious). In the latter case, the difference is enough to make me annoyed and to point out the disparity to my department Chair, but not enough to make me call a lawyer.
In response to my query, the department Chair gave me a significant raise, in part from supplementary funds provided for this purpose from higher levels of university administration. This raise was nice but not enough to bring me to the same level (or even within spitting distance) as the more highly paid coeval men, but it did close the gap a bit. I think the Chair wants to lessen the chance that I will leave and/or be very unhappy about the inequality, but he isn't about to do anything too daring.
What impresses me about my cousin's case is that her boss brought her and the other women up to salary parity. I think a lot of people in the same situation would toss the women a bit of money to make them less likely to sue but not do anything too "extraordinary".