You can look up RV values on NADA. That is what I looked at when buying my RV. I would assume with the current market no source is really that accurate. A dealer needs to make money. Guessing that RV values are going to drop over the next year or so they are going to low ball you just so they can make a profit should the value drop and they can't sell it for "todays" value. I would look at Craigslist, other sources where people are selling a similar year make, etc to see what they are asking. Expect a trade to be much lower than that value. You can try to sell it outright but you take a tax hit on the new trailer and you might not be able to sell it quickly. If you do, good for you.