What did the Internet cost?

Elizabeth sez,

Hey there. I'm a student of the School of Library and Information
Sciences at the University of Iowa. Our beloved sadist, er, professor
has asked us as a class to figure out how much the internet costs. All
of it, globally, from the very beginning. The electricity it takes to
run every server, every laptop. The salaries. The grants. The cost of
every bit of fiber optic cable in the ground around the world, every
little detail. God, I'm sure the catering budget for Apple would count
at this point. Right now I'm adjusting for inflation some of the
grants from the ARPANET days.

Part of the project is that we, proto-librarians, learn the research
process from the perspective of the most ignorant user. While I don't
like to pass judgment on my colleagues, let's be real for a second.
We're humanities. Most of us don't even know what questions to ask.
Boing Boing has scads of clever minions who I'm sure would love a
problem like this.

What say you? How much does the internet cost?