I went to a dealership to buy a Mercury Cougar when they were relaunched back in the late 90's. (a fact that I'm embarrassed about now)
After doing a test drive to make sure that it was what I wanted, I gave the sales guy my offer.
He looked at me confused and said "I don't know where you got this number from, but THIS is the price" while pointing at the MSRP.

I was horribly insulted and ready to leave at that point, but he scurried away to "talk to the manager" and left me sitting there for 20 minutes.
All that did was give me time to stew, get more pissed off, and resolve to buy the car elsewhere.
When he came back, he asked if I was ready to sign some papers if they'd give it to me for the price I offered.
I said "That's exactly what I tried to do 20 minutes ago. I will buy this car, but I'll be buying it elsewhere."
I actually ended up buying a V6 Mustang instead. That dealership didn't jerk me around, but would not budge from $500 above what I wanted to pay. (my number never moves). So I walk away, but get a call after I get home. "I'm sorry, we didn't realize that you were the husband of a relative of the owners, of course we can knock that last $500 off." Got the car for what I wanted, but was kind of annoyed that I needed to be related to get it for that price.
When shopping for a low mileage used car for my wife's aunt at the same dealership that had the Cougar, I scoffed at the price of the first car we inquired about.
The saleswoman said "You might want to try one of those dealerships with a gravel lot."
It was a friggin Nissan Sentra.

It's not worth 5k more because it's on a paved dealership lot. Her aunt couldn't find a used car she liked, so ended up buying a brand new one elsewhere. Might have been there had they not insulted us (again).
I used to work for a GM supplier. That was pretty nice. We had a no-haggle supplier price + any current incentives.
I'd just print out a paper at home and take it to the dealership. The only issue there was making sure you knew all the current incentives, otherwise the dealership would try to keep those for themselves.
My last vehicle was bought when GM was on the verge of going bankrupt, before the gubmint stepped in.
GMAC wasn't doing any financing and the future of the company was uncertain.
I made out pretty good. They seemed happy just to be unloading inventory.
I haven't dealt with buying a new car under normal circumstances in over a decade.