True. But this area, and the arguments that go with is, isn't just about the cost to copy a book (copyright). It's also about patent law - ideas were just as easy to copy back then. It's about copying plays, where the cost of copying the "book" is trivial, compared to the cost of the production itself.

I'm no historical expert, but I would wager that looking through history, you'll find that this situation isn't as unique as most people think. People were debating copyright in the English Parliament during the 1800's, including debates on piracy which practically predict the current situation.