Some private sellers are deluding themselves by thinking they are going to get close to MSRP for their used units. Some of them are asking more than what a new one would cost based on the discounts I mentioned above.
I quit posting when after all the pages of friendly comments and interesting discussion a couple folks decided to get sarcastic or decided to call Airstream 'trailer trash'. They are entitled to their opinions, of course, it just put a damper on the fun thread. But since you brought it back with some real world data, here is my take on the MSRP discounts and used values.
Selling used depends on how old it is and the condition. As prices of new keep going up it also helps the resale value. Keep one ten or fifteen years and it is possible the resale value could be near what it was purchased for new then depending on condition which is quite a bit less than what the new prices are today. Some dealers like George Sutton post MSRP of new and their discounted price. Start from the discounted price and get serious about the discount. Another ten percent will give the buyer around a twenty percent discount from MSRP. Anybody trying to sell a used one for what a new one costs is over the top.
Most used seem to hold on to a value (not necessarily NADA values) but asking price value of around two thirds of new three to five years old. At around the ten year mark they seem to be about fifty percent of new. A dealer will tell you almost anything to get you to think the price should be high. And how they are just barely making anything on the unit. Old game, they still play it. Then trade it in at a dealer and you realize what you have is just not worth much. It must work. Some apparently fall for the gimmic. Or some just want that new one so bad that they will take any beating on the one they are trading in.