Fare class, when you book all come into play.
I have seen silvers and golds on 800 dollar tickets to San jose upgraded 4/5 days out while i have to fight for a battlefield on a 425 dollar ticket.
They can admit it or deny it, but i have seen it 5 times now going to our corporate headquarters in san jose.
They buy B fares i buy the H fare and fight for the upgrade,