What I can understand from the facts you posted is they made a fair offer. They are is need of domain name and you are not using it at all. 11 years is a very long time and you are, willingly or unwillingly, blocking it for others. It will be good you not take this this to court and negotiate on a fair price.
Another alternative is, register the trademark in another category. In my country, there are 40 trademark categories. So making registration in any valid category should give you shield to protect the name.