But one should never let oneself be forced to name the first price in a negotiation. Particularly in this situation. Name a high figure, and there's a chance they will use it as evidence of your ill intent.
This is a pretty common script prior to a WIPO proceeding. You are being set-up my friend.
Let them name a figure first.
Better yet, get a lawyer. One that specializes in trademark law, and preferably with domain experience.
We can't even give you BAD legal advice, since we don't know the exact particulars of the domain names.