In addition to others, I have bought two used CVO's from the same dealer the past couple of years. A 2000 Road Glide with 11,500 miles and a 2008 "Casper" Screaming Eagle Ultra with about the same mileage. I know that this dealer uses the NADA book to price their used bikes, naturally they will try to start higher on the selling price, but they will deal at the NADA value.
Both times I made them an offer based on the book value and came away happy. On the 2008 I was also trading in a bike, checked the book and paid the difference.
Know what your bike is really worth before you walk in the dealership. If this dealer is not being fair, go someplace else. Of course, if the asking price can not be backed-up by Kelly or NADA it might not sell.
One of the reasons I have done it at a dealer is because I can extend the warranty easily or buy one if the current one has expired. Also, they do not have any sentimental attachment and believe it is worth more than it really is.
Just my experience.