Loads of cars are moved around in the collector world by this arrangement. A BMW place right out the back gate of my office does this all the time. See all sorts of cars come and go, and most of them are
The dealer has built a network and you are hoping that that network will appreciate your car, and or they will have a customer who has been looking for your car.
If they sell it they work out the deal, and you sell your car. They will most likely charge a fee, arrange transport, you can remain a bit anonymous and not deal with tire kickers, and people who want to test drive your car or just look about your place.
That can be worth the dealers take on a sale.
Out of my last three cars two of them where purchased via a similar arrangement. I know a guy, who knew the owner, who dealt with a dealer, all good networking. In the end everyone got what they wanted. I even got a fair deal to boot. And I picked some very epic cars in the process.