I disagree strongly that the connections are the source of the value, at least for undergrad. You're assuming that everyone who goes to an elite college is rubbing elbows with the wealthy. In reality, the people who are able to utilize college in this way are those who are already from wealthy backgrounds. Upper-crust kids don't go to Ivies looking to be "connections" for middle-class strivers.

I think that an elite college degree is worth $150k for most people, but I don't think it's the connections that add the value, so much as the prestige of the degree, the recruiting opportunities, and the information learned (mostly outside the classroom) about how the economy and society actually work.