Just brainstorming,

I got a .com that represent one multi-billion dollar company/fund in Europe. They want/need that domain name, because they only own local domain extension; however , they didnt make any official offers... They should hit me up with the offer in the next week or so. What would be counter offer that I should hit them up with after their first offer?

I am not going to name the company or the domain name.. but it's pretty big.
My problem is that idk how much do they need that domain, just because they dont have any competition. I am afraid to go to high, so they ll tell me to f off. any advise?