> If that is true, of which I remain highly skeptical, then it implies that books are wildly inefficient to produce.

It just means that publishers are really good at manufacturing physical goods. They've been doing it for several hundred years so no big surprise there.

Books don't sell in large quantities. The economics of scale for the publishes for labor aren't there.

No one is getting rich off of fiction publishing except for the rare break out author. Publishers go out of business (or get acquired) all the time because they are constantly one step away from being insolvent.

This is also why the industry has massively consolidated.

I highly suggest reading breakdowns of the finances of publishing books, it is an interesting field that is incredibly different than how we are used to seeing numbers work in software.