Service prices will depend on the
dealership in question. How much they charge depends on many factors, not least of which is how they feel on the day sometimes. Hourly labour rates affect also, and sometimes they mark up the parts cost.
What they actually do at a certain service also varies, as some don't do certain things and make up their own service schedule to suit the available funds. What should be done is documented in your service manual however.
Extras they'll charge for could be brake fluid change (which I've heard some dealers like to do after 7k miles!!!) which is due every 2 years, and an air conditioning service as and when they feel like it. Both of these are only advisory and shouldn't be done without your authority really so be aware before you give them the go ahead as to what they're actually going to do and what it's going to cost.
Brake discs are usually "lipped and pads wearing" so will need replacement. Check them yourself before they go in and then you'll know if they actually
do need replacing. My car went 20k miles with "brakes that needed replacing", and then they were ready to be changed.
Also, they could charge you for screenwash, regardless of whether they actually put any in there for you. A tale I heard was that a customer made sure his screenwash was topped up when it went in, and when challenged they said they siphoned the existing stuff out and replaced it. I seriously doubt that as that's just too much like work.
Providing them with your own oil is a good idea, then they don't charge you their silly prices for Castrol Magnatec (wrong spec aswell) and you know that you're getting the correct oil, that's if they actually use your oil and don't just tell you they did. The empty bottles back in the boot are usually a good indicator.
Be wary, and ask for a fixed price and breakdown of parts before you book it in. Some (and I stress some) dealers are awful, while others are much better. You could always consider doing it yourself, but then warranty issues may arise as it's not been documented service. Independents are also worth considering as long as they use genuine parts.