Given the fact that the upgrade offers don't count towards loyalty points accrual, I've actually found that the upgrade offers provide little to no value especially because in most cases the fare difference between Y and F is less than the upgrade offers I've been given. I was given an offer of $250 for each segment of a SANPHXSTL booking. Looking at the cost difference between my Y ticket and F on the same routing, the fare difference was $60; the only kicker was being charged the $20 agent booking fee since I was unable to make the change online. So in some cases the upgrade offers really aren't the best way to bypass the waitlist and get into F.