We tried to trade in a TT we previously owned. The dealer simply pulled out the ol' Blue Book and offered us whatever it said for the year it was produced, which was peanuts. Didn't matter that we had spent a few thousand on mods and upgrades or that we had only used it for one season and was in top condition. It was also a previous year's model at the time we bought it at a dealer and we lost one year's value out of the Blue Book numbers (ie., was valued as a 2 year old TT).
We ended up selling it to my BIL who happened to be in the market for one like ours and he paid more than the dealer offered. We did try to sell it on CL for a while but didn't get a single nibble. Selling a pre-owned RV can be tough, depending on where you are, time of year, state of the economy and the competition out there. Asking prices on sites like CL can be quite misleading because many owners think they can recover most of the original purchase price, which isn't the case.