I'll let someone else valuate the domain. But just remember that a (good) broker is replacing your time invested in finding the right buyer, replacing your effort in finding the right buyer, using their contact list and connections, as well as providing you with skillful negotiation.
Are these things worth 15%? To me they are, because I don't have the skillsets of a broker, nor do I have the time and knowledge to find the right buyer (if I had a name like that). But you might be in a completely different circumstance - and these, as well as your alternatives, are the things to analyze.