I recently booked a RT trip that included SJC-DEN-SJC as part of it. (Cheap L ticket.) I had to change my return a few days before the trip, but because the SJC-DEN portion fell on Memorial Day, the change fee would have cost something like $600. I decided to dump the second half of the ticket and buy a one way ticket as my return. Coach was $400 and First was $430. I happily paid the extra $30 for the EQM/mileage bonus and probably unhappily prevented someone else from using up e500s.