If I ever buy at a dealer, I will make it clear up front in the negotiating process my offer is an "out the door" price. Anything they want to add on after we've agreed to terms will negate the deal. I'm not into that s***.
But then, this is why I don't go to dealers, for the most part. That is the only way to negotiate with a dealer-out the door and no more! They can cahrge the $375 or whatever the doc fee is but they'll reduce that amount somewhere else or I won't buy. I never need a new car that bad.