Salesman are paid a commission based on the dealer's sales profit. The profit is typically defined as the difference between the selling price and the invoice price of the car. The most common car sales commission rates are 25 or 30 percent of the profit.So using a 25 percent commission plan, if a car sells for $1,000 over invoice, the salesman makes $250.ince the price a dealer actually pays for a car is a little less than the invoice price, the profit was probably $1,600 to $1,800 per car. This means that, using the AutoNation numbers, the average new car commission was $400 to $500.