> It costs roughly $1 for a professor to prop his camera up at the back of a room and record himself speaking for an hour... it costs $180-$600 to close-caption that video.

No, both of your figures are wrong. I actually worked in UC Berkeley lecture recording and captioning, and the figures are on the order of magnitude of $10/hour for each. The problem lies in the massive backlog of older courses that would need to be captioned for only a few non-students per course.