On-campus housing is pretty good and the prices seem reasonable. You'll probably pay about $650 per month if you live with one or more roommates. An on-campus studio costs $1,000 per month (even if you want a studio, you may not get one--I think the demand exceeeds the supply by a pretty wide margin). If you don't meet anyone you wish to live with during the admissions cycle, the university will match you up with other grad students based on shared preferences expressed on your housing application forms. Everyone I've met seems to like the roommates they were matched with.
The main additional expense of Stanford is transit-related. Most people want a car so that they don't have to walk for 25 minutes (or catch a bus) to get into town. But if you do have a car, it's also easy to get to San Fran, the beach, or the mountains. That's hard to beat, and I'm considering buying a car to take advantage of those opportunities.