I now only buy slightly used cars, say 2 or 3 years old, non-rentals or fleet cars, with some warranty still on them. But I once bought a custom order Ford Explorer. I went in with all the options I wanted, and went to numerous different Ford dealers to see what price they would offer me. I got what I thought was a fairly good deal from the second dealer I saw. The next 4 dealers all refused to meet the second dealer's price. When dealer number 6 said that the second guy was making only about $200 off me, I went back to the second guy and finished the deal, as I was confident that the price he was asking, was reasonable.
Is there a lesson there? Maybe that if you shop around, you can figure out what the best price you're going to get for that particular vehicle is. The lesson I learned was, don't ever buy new. Slightly used, if you've done your research and shop smart, is the way to go. And keep it for 10 years.