Originally Posted by
ijgordon
Almost nobody voluntarily buys a higher fare class. .. To get a higher class for higher upgrade priority is foolish.
I think you underestimate the amount of people who will upfare from an R or A fare to O in order to try and move up on the upgrade priority for Polaris.
Originally Posted by
ijgordon
To buy up to YBM probably costs more than just paying for P unless the lower coach classes for the dual-inventory fares are sold out.
YBM isn't intended to buy up to get an upgrade to J (because if PN is available, there is probably a pretty competitive buy up offer as is). YBM-ups are intended to reward people who have to buy what are considered full-fare economy, either due to booking close in, employer policy prohibiting purchasing business/first class outright, or in order to have a valid booking code/combinable fare with a premium fare elsewhere on the itinerary.