That is crazy. This whole fare class thing drives the reality of the flying experience and United continues to hide and screw it up so that you can't tell what is happening.
So is one a P fare and one a some kind of P made up from a Y cabin fare? 58 versus 926 a UA versus Continental thing?
The P fare multiple seemed like an elegant way for UA to give higher than flown status to people that pay for higher priced tickets. Fly P fares on a few overseas flights for over 50k BIS and make 1K. Really kind of a poor-mans GS because if your company will pay for P, you can use your GPUs for personal use.
I don't know how common it is, but my company buys Y and I'll come back and go with the higher F class fare as a change. Seems like that isn't that uncommon here.