This is true, yet the cost is not calculated this way. It is not only the print cost. Large publishers have overhead cost that can exceed the publication cost itself such as the different departments, legal issues, marketing, renting for booths...etc. While the self-publish look promising it face lots of barriers. Most self-publishers can hardly sell their books as they focus on writing and neglect other factors such as marketing which make take equal effort and more cost comparing with the writing itself.