Almost no one pays cash for a car anymore and the industry knows this. Many dealerships make more money (or at least they did, but I'm sure they still do) from getting people to get a loan from one of their "partners" (auto-loan companies which accept their paper). It's been years since I worked for an auto-finance company (my soul still feels a little dirty), but I know it wasn't uncommon for dealerships to get an additional 1-2% from the loan. This gets complicated as far as how much they earn per car, because there were also penalties for loans they sold that defaulted before a certain point etc. In the end it worked out in their favor though hence why they kept using certain loan places. This is why you hear people tell you always negotiate the price of the car before you tell them you have your own financing (either cash or through your bank), because they'll drop the price a little more knowing they will make it back. Don't ever think they're working to get you the best deal possible either, they'll either give you the first response they get back, or the one that nets them the most money if multiple ones come back at the same time. The faster they get you to sign, the faster they get paid.
(I also really hate to say this, but if you're female and don't like confrontation, bring a male friend and act like he's the one buying the car. It's a male dominated industry that is very sexist. If you're a strong person and can handle it by all means go for it, but expect them to be pushy and talk down to you. I'm a white male, and I hate dealing with a lot of them. I can't imagine, although I've heard the stories, of what it's like not being in the privileged class.)
The real truth is that to the dealership, this additional money doesn't really matter in the big picture. They make almost no money from selling cars. You ever notice how all the dealerships have a service department? That's not by coincidence. It used to be (and probably is still close) that 90% of all revenue from a dealership is on service. Getting money from warranties; getting money from people who only trust where they bought it etc. They want to sell the car, so they can get the maintenance. They won't sell for a loss, and they'll take you for what they can, but really they're in it for you as the long term support. Also, the car salesperson has no real influence over the price you get. That comes from the general manager behind the desk. (A long time ago this didn't used to be true, but dealerships wised up that you don't trust people on commission making decisions. It's quite possible the sales people don't actually know the true cost of the car to the dealership.)
You want to hear about people signing things they don't understand? I really wanted to scream at people after I heard this story. There was a hispanic couple looking to buy a car and they didn't really understand English. The car salesman told them if they signed the contract, they could drive the car as much as they wanted. He neglected to mention to they actually had to pay for the car, and so they took the deal. You can guess how that worked out. Course the salesman didn't care; he got his commission. I'm not saying they're all like this, but some of them are complete trash.