I just sold a 6 year old Clydesdale, just halter broke, for a decent amount. There were no shortage of inquires either, even though he was a project that needed lots of work. I don't know what sales are like in your area. My cousins bought a nice yearling filly, unregistered, for $1000 a few years ago, and that seems to be an average price around here, lots between 1000-2000, and up if broke under saddle or harness, not much under 1000.
I would say price him at 800 negotiable and see what happens.