Unsold cars on the lot are burning cash, as they're there on borrowed money.
BTW, he had to get the manager's signoff on the final price, so I'm sure he wasn't getting fired for it. A savvy manager isn't going to let a salesman underprice a car to sell to his buddy.
You mention a lot of considerations, all perfectly valid. That's what makes the game interesting and fun :-) I'm sure the salesmen also size of the customer based on his clothes, the car he arrived in, his demeanor, etc. I remember shopping for a new car long ago, arriving at the dealer with my usual worn out jeans. None of the salesmen would talk to me. So I bought the car from the dealer's rival. These days, Seattle is full of millionaires wearing jeans, and the salesmen know that, and don't make that mistake.
