Why aren't Christian books and Bibles FREE?

I've always wondered why Christian authors publish for profit books. Here's the copy right for a book about sustainable energy that I recently purchased.

This is a free book

I didn’t write this book to make money. I wrote it because sustainable energy is important. If you would like to have the book for free for your own use, please help yourself: it’s on the internet at www.withouthotair.com.

This is a free book in a second sense: you are free to use all the material in this book, except for the cartoons and the photos with a named photographer, under the Creative Commons Attribution-Non-Commercial-Share-Alike 2.0 UK: England & Wales Licence. (The cartoons and photos are excepted because the authors have generally given me permission only to include their work, not to share it under a Creative Commons license.) You are especially welcome to use my materials for educational purposes. My website includes separate high-quality files for each of the figures in the book.

Here is a man that is passionate about his "cause" and is anxious to get his message out, so much so that he will give you the fruit of his hard work and encourages you to use it in your own materials. I guess sustainable energy is so much more important than a person's relationship to God.

The first couple of sentences tell the tale. David JC MacKay is more like Jesus than most of our popular Christian authors. BTW, I purchased David's book and I would continue to purchase Free Christian books. It's just that they should also be free. Free to read, print, use, etc.