Sam,
Here is a link to the NADA guide for your trailer. It is base pricing and note that it is for "retail" - not what you will get for a "trade in".
https://www.nadaguides.com/RVs/2018/...6578571/Values
The dealer is playing the same game every car dealership plays, and I've played it many times. They have a margin that they are going to make and they know what they have in the new unit....you don't and you aren't going to find out no matter what they show you. They also know what they are going to sell your unit for after they look at it...you won't no matter what they tell you. If you shoot for their "rock bottom" price in the new unit (which in this case seems pretty high - I would go for 30% off msrp) they are going to give you "rock bottom" trade in. If you go with msrp they will give you the "high end" for your trade in. Either way the margin remains the same; you get to walk away thinking what a great deal you got on the price of the new trailer, or, what a smoking deal you got for your trade in. In reality it is very difficult to walk away with both.
Right now in RV sales they sell them as fast as they can make them. If you don't buy it someone else will if it's a decent floorplan and not priced in the stratosphere. They depend 100% on your (or the next customer's) driving desire for a new trailer, "that" trailer, and your willingness to compromise and spend the dollars even if they are making a little more than we want them to. If you don't do it, the next guy will. It's just the nature of the beast so go into the negotiation hoping for the best and expecting the worst and set the limit in your mind on how much you're willing to "give" to get the new trailer. On the other hand, I personally would sell the trailer myself to save the bath your going to get by trading it in.