Hi jimlad,
I have heard ( on
www.v-flyer.com) that for the East coast of the USA flights ( and IAD -Washington which is the VS21/22 route) that upgrades at the ticket desk on the day of departure could be had for £199 each way.
Of course you are then relying on the upgraded seats being available ( ie PE not full on the day)
Good luck
Regards
TBS