Originally Posted by
VegasGambler
The problem is that there is no one price for specific inventory. The issue is that they need to use historical prices, not walkup prices
If you purchased an I fare with an underlying, say, Q coach fare, they know exactly what the difference is embedded in the fare. They don’t even need to look at the coach fare on the rebooked flight.
It’s usually a fixed up-charge regardless of the coach fare, if you’re booking in I inventory. If you are booking in D, then the up-charge is higher.