Specifically with regard to vehicle sales, dealerships absolutely do not pay invoice price. Between dealer cash, customer cash, holdbacks and other financial things, it is all but a made up number.
"We spend a month at a Jeep dealership on Long Island as they try to make their monthly sales goal: 129 cars. If they make it, they'll get a huge bonus from the manufacturer, possibly as high as $85,000 — enough to put them in the black for the month. If they don't make it, it'll be the second month in a row. So they pull out all the stops."
http://www.thisamericanlife.org/radio-archives/episode/513/1...
"We spend a month at a Jeep dealership on Long Island as they try to make their monthly sales goal: 129 cars. If they make it, they'll get a huge bonus from the manufacturer, possibly as high as $85,000 — enough to put them in the black for the month. If they don't make it, it'll be the second month in a row. So they pull out all the stops."