We didn't get an extended warranty, but one extra charge we did get was $1000 for NOT getting financing. (We had the money saved up and gave them a certified cheque.) In hindsight, I wish we'd gotten the darned financing, saved the $1000 fee, and then paid it off immediately (unless, of course, there would have been a $1000 early-payoff fee!) This all makes my head hurt.
That $1000 charge is one reason why I'd never go back to that dealership (topic!). Another is that, when I asked how much of the car I could put on my credit card*, the guy got very huffy with me as if I was trying to pull something shady.
* The only reason I wanted to put it on my credit card was to get the cashback - as I said, we had the money saved.