Sometimes, the expensive schools and most notably the Ivy League schools, offer valuable networking opportunities that add to the value of the degree.
As much as I hate to use the term, yes, networking can be a big part of it. I certainly made connections in my field that I would never have had contact with at say, Fresno State. Also, in my field, I had access to hardware and labs that most state schools couldn't afford.
I will say that I think the school/dept makes more of a difference in thiose areas with advanced degrees versus an undergrad degree. It's also only part of the equation, with the student being a greater part. On the graduate level, if doing an interview, I would pay more attention to the Podunk grad that had a 4.0 and examples of well done graduate research in his resume vs the "well known school" student with a 2.5 who did nothing more than the bare minimum of a thesis or simply tested out. At least in the sciences.
Also, I have mentioned this in the past, but some of the Ivy league schools will graduate their students "no matter what" to protect their reputation, as drop outs apparently hurt that rep. Example given by an ex girlfriend that was a Harvard Law grad and said that that Harvard would push them to graduate regardless of their ability, and even setup their bar exams in easy states, just to add another lawyer to the alumni list.