What I meant is zero cost of production, I guess I didn't articulate that well. And yes i know the labor from the author editor etc. is a "cost" but the e-book itself cost nothing to produce.
Beyond what Sigyn said, the problem with this mentality is that you're inappropriately separating the cost of producing the content of a book and the cost of producing a copy of that content. Yes, it costs relatively little to produce eBook files, and the unit cost of distribution is negligible. However, if you price eBooks with only those factors in mind, you're not recouping the cost of producing the
content of the book, which is the largest expense involved with any book.
Why should print books subsidize eBooks? That mentality devalues eBooks and relegates them to second-class citizens in the eyes of consumers and publishers. If we keep that mentality, nobody can ever buy
all of their books in electronic format, not least because publishers wouldn't be able to survive if they did, and the eBook market would remain a tiny niche.