I have, on several occasions. I've been that upset person once, even.

I know lots of people who are dissatisfied because they're obviously far more valuable than a peer at the same level, and lots of people who are resented because of their parasitism at a higher-level job. (This is in the government system, where salaries are pretty transparent.)

And that's exactly how it should be. If you're far more valuable than a peer but are being paid the same or less, you should be dissatisfied. Ignorance may be bliss, but I'd rather know I'm getting shafted so I can either renegotiate or look for a better opportunity.