i hear both things, but people are generally wrong, no matter which way they believe it went. a lot of people really believe dealerships make tons of money on new cars (spoiler: they don't), and then there's a lot of people who believe that if they pay under invoice, they must have gotten a damn good deal (spoiler: they probably didn't).
but again, it is really easy to figure out approximately how much dealerships are paying for new cars. try to control for the cost of extras (spoilers, navigation, etc), and then just see what the average cost is in your area. on fords, odds are that their margin is about $1k. new cars are easy to figure out if you just put the time into a little online research.