There are a couple of people that have registered the majority of extensions on this, so one of those two may really want it or need it enough to pay a nice amount. This isn't really about appraisal - the name itself isn't that fantastic, it's all about negotiation and knowledge. What you need to try and figure out is who wants it, what for, and what do you think they will pay for it. You have to do some research and see if you can figure that out - or just shoot really high and see what happens. If the offer is less than X,XXX you may want to just reply "no thanks, I think I will hang onto it and develop it" and see if they increase the offer. If they offered X,XXX or more, counter with a nice five figure amount and then work back from there if it is worth it to you.