It's not that big of a job, but if you are talking about the dealer doing it they just go by the book. It will allow so many hours for each individual job, and that is what they charge. Regardless of how long it took the actual tech to do the work.
Yeah... they use book hours because that's the law. Go figure. Automotive repair shops and body shops do the same thing. Of course, no one complains when the tech works on the vehicle for 8 hours and can only bill 3.5 book hours.