I have never heard of anything like that. Ever. I've heard offices charging for weird things but every single time you walk into a room it is supposed to be sterilized. The insturments, chair, counter, light... all of it.
I'm sorry you went out of network and have to pay more out of pocket but I wouldn't want someone I don't know looking in my mouth and telling me whether or not my mouth is ok if they aren't a professional just like I wouldn't want someone who knows nothing about framing a house building me a house. You pay for the supplies used (and the supplies aren't really cheap if you got a white filling), the time, and more importantly the knowledge.