"[T]he trade-in cost for my car they offered was literally half its market value."
I'm curious why you'd expect them to take it for more? They wouldn't do trade-ins if they couldn't profit off of them, and you can't buy things for market value and run a successful business.
If you want close to market value for your car, you have to sell it yourself. And if you think about why you didn't do that, you can see why it costs you something to do a trade-in.
I expected a bit more than 50%. Anyway, my argument isn't about trade-in sales, its about typical profits of dealerships. They absolutely do not make "only $200" per car. When you factor all the things they typically do, they can and easily do thousands per car sale.
I'm curious why you'd expect them to take it for more? They wouldn't do trade-ins if they couldn't profit off of them, and you can't buy things for market value and run a successful business.
If you want close to market value for your car, you have to sell it yourself. And if you think about why you didn't do that, you can see why it costs you something to do a trade-in.