@Pamela Jo,
The purchase price has nothing to do with printing. Most of these articles are distributed electronically, though operating the publishing platforms is not cheap. The price is whatever the market will bear. Even if they are printed on paper, the selling price is out of proportion to the cost of printing. For instance, the book I did for ALA Editions is a few hundred pages long, a paperback, and they are asking
As for publishing a lay edition of an academic paper, normally copyright ownership remains with the author, and authors often publish numerous papers based on the same research. For instance, an article for a peer reviewed journal, a blog post, a chapter for a book. They want SU$68 for it. My grandson buys 1,000+ page science fiction by Brandon Sanderson for US$7.95, or so he tells me. So, the publisher is not worried about putting ink onto paper.
Unless your husband has signed a contract giving ownership of his expertise to the publisher, he is within his rights to use the same ideas and references however he wants.
Now that you have my interest, I'd love to know more about him and his writing.