It is a business, plain and simple. They exist to make money, not be fair and trade fair market value for fair market value. Especially if the vehicle they are selling is a brand they represent, they will most always be charging a premium on their used vehicles, and may or may not pay good money for yours.
The more a vehicle costs, the faster it depreciates. This is especially true of vehicles that are basically the same. A fully loaded Golf may cost upwards of 10K more new, but in a few years, all those extra options like automatic transmissions, sunroofs, tech packages etc etc do little sometimes to increase resale value, rather it is exterior shape, mileage etc that influences most buyers.
I agree, dealerships can be very frustrating.. But in the same breath so can customers who want the world for their vehicle, and want a bargain on theirs. At the end of the day it matters little what a dealership paid for a vehicle and this should not be factored in to your bargaining unless the dealer is also your uncle. All this does in the end if they have more gross is perhaps to show you more on your trade if you have one. If a dealership has too much tied into a vehicle it can be difficult for them to move.
There are lots of tips on the interwebz on dealing with dealers.. Kindness goes a long way. If someone is a jerk, what is their motivating factor to do anything for that person?? Especially if there is little gross to be made. Salespeople typically do not make money on the trade, only the sale, so their is not much incentive one way or another, unless they have to take out of the gross to pad your trade value.
Why not just sell your vehicle privately? should be an easy sale if there is nothing wrong with it. If it is not an easy sale, or you have been trying with no success and now want to trade it in - you are asking the dealership to take the burden of stocking a depreciating asset, another reason why they pay less than current retail market values..
The one thing I never understood is why so many people get their feathers so ruffled expecting a dealership to heavily discount their vehicles.. I mean think about it, the vehicle has what maybe 5 to 10% gross profit AT MOST! And people expect to buy at invoice all the time?? Tell me the last time you walked up to a cashier and asked for a discount on your eggo waffles and creamed corn. And those items have over 50% markup any day of the week!
Anyways, I think I am digressing lol
ps - why you want to dump the Autobahn?