It should be priced like a 2018 model. Check prices for similar used units, and consider what an extended warranty plan would cost on a used 2018 model and add that price to the fair market value of the used unit. That price, plus a small mileage allowance, should equal what you are paying for that new 2018 model. I doubt a dealer will discount the price that much on his new unit! Also, your purchase inspections should be just like buying a used 2018 model. The previous posts about inspecting caulking, tires, batteries, and all systems are very good.
In essence, you are buying a unit that is at least several years old and has been used by the dealer to show to prospective buyers. It is a used unit in that respect. The previous post about it being a used 2018 model as soon as you drive it off the lot needs to be considered seriously. What will your "new" 2018 model be worth 1 month after you buy it? Your purchase price should not be greater than than figure!