It's a bit cheaper for an apartment, in most areas, if you have a roomate or two. If it's just you then it's cheaper to live in a dorm.

I'm moving onto campus next month, though it's my fourth year of school. I refuse to stay in a dorm though. I'm moving to the on-campus apartments where I'll have my own bedroom, and have three roomates with their own rooms, and we'll share two bathrooms, a livingroom, and a kitchen. That, plus all utilities, cable TV, and cable internet is $600-something a month, but I get financial aide so it's gonna be $200 a month for me.