In my experience NADA guides run pretty high. They are intended to justify a dealers posted price. That assumes the dealer has corrected all flaws etc. Even then you expect to get 10-20% off that price. I would say the private party sale price should hit more like 20-30% off NADA.
Then you would deduct for signs of damage etc.
This is nothing more than opinion, but I think a more fair sale price on the unit you are looking at would be close to 6K. The price you quoted just seems way high to me. You could step into a 28BH Grey Wolf for only 4500 more than what you are talking about.
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