FlyerTalk Evangelist
Join Date: Feb 2009
Location: From ORK, live LCY
Programs: BA Silver, EI Silver, HH Gold, BW Gold, ABP, Seigneur des Horaires des Mucci
Posts: 14,214
I think that's a bug with the BA website. Check if booking WTP outright for the same dates would cost the same amount that's being asked for the book and upgrade. If not, then it's bugged.