I don't get it, no one here ever leased or bought a car? Anyone who leases or buys knows that there will be hidden fees thrown in, and yes we hate them and their wrong, but that is how the car business is ran, and we all go and get cars. If it's that wrong that they charge you more then they advertised (or even promised you personally) then you should sit without a car, why is it that everyone gets cars? Very simple WE NEED THEM!
Car dealers are known to be crooked, people dealing with credit card are known to be "shady", if you really need the 4k you'd accept it even though you were promised 5k. I'm not saying it's right, in fact it's absolutely wrong of the guy promising, but if someone desperately needs it they might consider accepting the "loss"