I agree, but there are something like 250,000 books published each year.
At just $5 per book that's $1,250,000 just to buy each year's worth of books, never mind the staff to do the buying and unpacking and cataloguing and stocking and lending etc etc.
 (http://en.wikipedia.org/wiki/Books_published_per_country_per...) (but go careful because who knows where the wikipedia numbers come from)
 A ridiculously low figure. Here's some UK data; not sure where it comes from. (http://www.holtjackson.co.uk/cgi-perl/web_avg_book_price.pl)