No kidding about the dealerships. I was purchasing a new car once and the Finance guy kept saying "Just one more thing and then I won't say any more about it...", but he did that more than 10 times. I was trying to be polite, but I finally said: "I'm willing to get as angry with you as you need me to so that you'll shut up about this" and he finally quit. Whew!
I had one dealer wait until I was out of the room (I went to the restroom) during which time he had my wife sign it and then tucked it away so I wouldn't see it.
They are really snakes. You have to be on your toes and watch them every second.
When I purchased my current truck, I told the sales guy that when we go to the finance guy, I'll allow him to press the extended warranty 3 times and that's it. If he violates my limit, we're walking out. As a result, the sales manager finished our purchase - I never saw the finance guy. Perhaps they didn't trust that he could keep his mouth shut
Of course, they can tell you're being extra careful and always say "don't worry, we're honest here - you can trust us"