7g a 20G sale, whiskey tango foxtrot have you been smoking. I also sold in the eighties. I was always in the top five from 87-90 in largest dealership in AZ. While 4g seems right on the front end. In reality it rarely ever happens. A 3G figure on the back had to include projected warranty service.
Sales managers do know true invoice, its their job. The work for bonus. There bonus is based on monthly sales revenues over the dealership fixed costs. Sales managers are always keeping a running tally of profit over invoice on every sales day. Its their job to refuse a offer and inspire the salesman to go back and sell the terms that the sales manager is looking for.
In todays market, Dealerships make from 1200 to 3G on new sales. Used the sky is limit depending on model availiblity and popularity in the given market.