I had this issue when looking... The dealerships are looking to get near MSRP, due to the fact that the vehicle never sold... they are out the Invoice price... so they are still trying to make some coin.
Best bet if you really wanted that vehicle, go in tell them that even though its a DEMO vehicle... it is still classified as used due to the fact that it has been registered.
This would make them upset, as they are going to be loosing out.
Go in offer them what you think is fair, for a used vehicle with that mileage. if they say your crazy, just give them your number and tell them when they can be reasonable for the purchase of a used car... they will call..
It helps to be on the phone with a Nissan or Honda dealer when you walk out
(almost had to do this with mine, but for the price that they wanted for a used... i got a new for $4k more, with ~20 mi, with the options I wanted)