i bought mine for 350 but it had only been used a few times (on Hemir, as it was bought for him!)...was bought for 600 but had a small scrape at the back where her son had dropped it - when putting it down he wasn't very careful. She even had the reciept saying she had only bought it 3 months before! That was a year ago...sorry don't know how much you would get for it.
What model is it? how long have you had it? Is the gullet changeable? any photos to see the condition? and what size seat is it?