I sold our older unit earlier this year and bought a used one a few weeks ago, both as private-party deals. Maybe I'm just too far down-market, but I tried using the Good Sam valuator a couple times and all it would ever do is want to collect more information and have someone contact me. Hard pass.
In order to figure out where to price mine and what price I was willing to pay for a new one, I spent several months scouring Marketplace and RVTrader and put together a spreadsheet. I had the basic model information, the asking price, what JDpower thought the price should be (I only accounted for mileage, not options since those can be really hard to figure out), as well as a few key features that we might have wanted to use to sort. I'd go back and revisit the entries periodically and mark down the date that they sold and record any price drops - there were actually a couple that had price raises, which I thought was weird. In the end, I had over 250 coaches recorded and that gave me a really good idea for what the market looked like. Granted, I didn't have any actual selling price information, but I could see how quickly coaches at a given asking price were going from listed to sold and how many price reductions they went through and could sort of extrapolate what constituted a fair price. As a small bit of anecdotal evidence, I sold our old coach for more than what JD Power said it was worth and I also paid more for the new coach than JP Power said it was worth. In both cases, all parties were happy with the transaction and I don't think I could have negotiated another coach of the same type in the same condition for much less.
I guess what I'm trying to say is that in my experience, it's not like trying to put a price on 2017 Camry where there's a hundred of them running through auction every day and the conditions are essentially the same. You might be able to use JD Power as a starting point, but your best bet is probably to do some research for models of the same type as well as models of a similar size with similar features and try to extrapolate a good starting point from that.
