Upload & Sell: Off
personally, i would'nt necessarily "double" it. for example, say 20x30 is $100 (framed and all) and you charge $200. Then 30x60..costs $200 ...charge $350~375.
It allso depends on # of prints, do you want repeat business etc. If its small quantity, naturally no discounts. if its multiple you would want to factor that in...unless you're not getting a volume discount from your framer.