Quote: "You must pretend that you invite people because you want to celebrate important occasions with them, and you must seem pleasantly surprised when they give you something." Miss Manners' wedding advice
Figure of Speech: accismus (ak SIS muss), the oh-you-shouldn't-have figure
If you're cheap or greedy (and Figaro admits to being both), the accismus -- a fake refusal -- is your figure of choice. Latin for "coyness," it makes you look like less of a jerk than you really are.
Snappy Answer: "Oh, we don't want a gift. A check will suffice."