Yeah. As someone who's not used to negotiating regularly, especially at car level stakes (what else do people buy that's expensive, houses?) buying a car from a dealer was an experience.

The war analogy is apt. Burn every bridge. Don't just be ready to walk, walk. It's an all day process, but it can save you literally thousands of dollars. One of my old managers went to the lot, looked around for the least saleable car, and made a standing offer for it. They called back a couple of times with higher prices, he declined. Turns out at the end of the month, they have to make a quota and would take his deal.