The dealer knows how much profit he is willing to sacrifice when dealing with trade-ins. He has to cleanup and prepare the trade-in for resale, advertise it, pay a commission when it's sold and etc. So he looks at it as ACV Actual Cash Value when figuring the profit margin of the rig you are buying.
As far as LaMesa of Tucson goes, I have first hand experience with them. We bought our new Winnebago Vectra from them, the rig we had prior to going with the Montana. The service work was horrible. We had the list of things that needed repaired as all new units have. And we set appointments, often having to leave the unit there for days on end. When we would get it back the things were not fixed or not fixed right. This was upsetting and when we took it in the last time, I discovered in the electric bay a number of wire bundles and wires just laying in the bottom not secured. We called Winnebago and had to drive to Forest City, Iowa, to the factory, to get the warranty items fixed. I realize this comment has nothing to do with your trade in question, but feel obligated to pass on to those I find out are dealing with that dealer and location what our experience was. Now I can sleep better tonight. Buyer beware.