e-books

So I'm in the engineering library right now looking at this poster that lists ten reasons why the internet can't replace libraries. Number 5 says that a state (American poster) can't buy one book and distribute it to every library via the web. The only reason given is "We all want to save money but this isn't the way". This is hardly what I'd call an explanation. I imagine the real reason has to do with the legality of the process.

The one that bothers me the most, though, is number 8, which states that digitizing 500 000 books (a decent sized library) would cost approximately one billion dollars. Don't publishers already have books stored in some kind of digital format for editing, and especially layout purposes? Don't modern printing presses print from computer files, or are they just some sort of giant photocopy machines? If publishers already have digital format texts then I don't see what the practical problem would be (obviously there'd still be legal issues). The only problem would be out-of-print works.

I know that some of you (e.g. Caitlin or Swambo) know a lot about the publishing process so I'd appreciate it if you'd clarify this for me.