United is offering an upgrade on my flight from L class (economy) to J for 20k miles + $250 (standby upgrade). Is this a good deal? I paid $184 for ticket, and J flights that date on any carrier are about $1,100, with no saver J available. Is this a good deal? Are my chances of actually clearing on this upgrade better, or worse than on a "Plan B"?
Also, do any UA upgrade certificates work ? The option is currently grayed out, but I'm not sure if that's because it's unavailable, or because I don't have any.