Both NADA an KBB have a ludicrous list of "extras" that can be added to the price. When we were shopping, I saw things like a kitchen and its appliances, holding tanks, potable water tanks, propane cylinders all listed as extras and adding to the supposed "sticker".
We ended up buying a used 8-year-old rig from the original, very fastidious owners for a price that was well below (maybe $9K) the silly numbers in KBB. It end, it turned out they'd had so much enjoyment out of the motor-home in 8 years, they were prepared to sell for what was left on the home equity loan they'd originally used to finance it.
They were satisfied, we were happy and we got a good quality RV for a reasonable price (about $8K below the "silly" numbers and about $3.5K what similar rigs were going for at local dealers.
We found the rig in our local paper. The sellers were about 30 miles away.
BTW, we also used a home equity loan, like the sellers had, to finance the deal. Our Credit Union was very accommodating and we got enough to cover the sales tax (almost $3500) and a new set of tires ($2300) and a bit left over for our first couple of trips. They didn't even ask what we were buying with the money! No arguments about NADA or KBB numbers, as we had about $150,000 equity in the house at the time.
