I think it may depend on brands and models. When I take my specific Honda in for the scheduled maintenance, the dealer seems to apply a standard, Honda-dictated price, which is the same at all the dealerships I've visited. This usually includes the labor and replacement for the parts which the manual says need replacing on a schedule, except for fluids. If I need tires, brake pads, that's separate.

I know this is a fixed price because last time I took it in, it was a "bigger" service, where they had to check valve clearances. But apparently something went wrong when they tried to take apart something (I forget the details) so they had to work much longer than expected on it. In the end, I didn't have to pay more than I had expected, taking it in.

Now, all this isn't to say it's cheap. I was horrified with the prices: it often costs more than my Mercedes' service at a Mercedes dealership.