Bottom line, you are looking at a 9 year old trailer that probably wasn't the top of the line model when new. High NADA would have to be for a trailer in like new condition including all appliances, not a blemish anywhere, and then you still have 9 year old appliances if they haven't been changed out. $2500 above high book is not a discount. The dealer paid to much for it as a trade in. That's his problem. For that much money you can do a lot better with a newer trailer.
There's nothing here that make this dal look like it;s in your favor, but if you early think this is the trailer for you, I would have an independent that doesn't have a dog in the hunt do an inspection/appraisal and believe what he tells you. A lot of buyers get burned on love at first sight deals and this dealer has ben in the game lot longer than you have. Proceed with care.