[wwweston]

I suspect the pricing of the book has less to do with any judgment about the features and relative superiority of the delivery substrate, and more to do with the economics of authoring a worthwhile text, which require a risky up-front investment of time few authors have any reasonable assurance they'll see a return on.

So most of the cost is probably going to paying the people who produce the book and repaying investors/publishers.

[bhewes]

Spot on. I have been involved across multiple publishers. The cost of the book is normally set by whatever is needed to pay the editors and authors to produce a quality book. And the continuation of the publisher.