There is another side to the new versus used discussion. On another forum I see a couple bought a one year old unit with only 6200 miles and the dealer just lied through their teeth about the rig. Customer ended up with massive headaches on his "gently used" motorhome. If someone dumped it, there had to be a reason and you may not know what that reason is.
Depreciation from MSRP is a difficult analysis because different units have different margins. Entegras can generally be bought for at least 30% below MSRP and closer to that 35% mark while Newmars tend to be closer to 25-28% and the same with Tiffins. It is very difficult to evaluate the depreciation based strictly on MSRP.