I don't think, that you are free to set your own price. But of course, I am not current in these special law topics. But in Germany, as in many other countries: If it goes to court, you will loose against a big company.

It was an other situation, but a lawyer once told me, what happens when such things go to court: The corporation will bring 10 witnesses against you and will bring 10 experts certifying what the corporation needs.

And than you will be very alone and be gracious to get even a little money. You will loose your job anyway.