Originally Posted by
Bonehead
I routinely book business trips in Economy in order to generate a receipt for the expense report and then immediately change to flight(s) to FC. It's been my experience that the upgrade offer is rarely < the upfare cost. Equal...at times, but not usually.
It will be lower when only higher economy fare buckets are available, since it's calculated based on the underlying fare differential. So if you bought a T and now W is lowest available economy, the upgrade will be cheaper than the upfare.