If the ads talk about a specific vehicle then those are called "Loss Leaders".... most retailers (cars or otherwise) use them. They're used to get the customers in the door.. sure they might lose money on that ONE sale.. but they'll more than likely make up for it on the sale of vehicles to people that came in to buy that ONE vehicle.
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The Iron(FE)-Works
My daddy always said, "When you want to hammer a nail, don't do anything fancy. Just get a hammer and pound the son of a bitch."