Being close to the used car business for many years, knowing salesmen and sales managers socially, I can tell you that "hunger" also comes into the deal. These guys work on commission, and the longer it has been since they've had a decent paycheck, the more willing they might be to trade off some of their little share of the pie to keep you from walking out the door. But if they've had a couple of good weeks, they might be more likely to hold out for more margin and a bigger commission, because the next guy to come in the door might be looking for exactly what they have, and pay the asking price to get it.
So thebest you can do is to know what you want, and what you want to pay for it. If you can't get it for that price, be ready to walk. If you do get it for that price, don't be worrying for the rest of your life that you might have been able to pay a little less.
