My mercedes dealer charges 120 for an oil change. Also, when they're changing your oil they do a complete inspection of the car.
You expect them to do it for free?
If I did use a dealership for basic maintenance I'd expect them to do only what I'd asked them to do.
do you want the handy dandy 23 point inspection as well or do you just want your oil and filter changed? If the former, sure pay for it. If the latter, you should ask and pay for only an oil and filter service. If they won't give you a price just for the oil and filter, that would of course be typical car dealership bs and a good reason to go elsewhere.