Does it matter what your other colleagues earn if you were once happy with salary during negotiation?

The Siz The World team weighs on what to make of the passing of legendary actor, Robert Duvall and recounted an interview Duvall did on why he did not appear in The Godfather Part III because of a contract dispute regarding a significant pay disparity compared to Al Pacino, not because of the script. The team ponders on whether it should matter what your colleagues earn if your were happy with your negotiated contract from the onset.

THROW OUT: Why would it matter what other people earn, if you were happy with your initial contract?