If your opponent is also gaining some revenue in your theoretical situation, sure.

The ultimate point of the book is to gather support for legislation that would give teeth to antitrust. It needs to reach sufficiently many people for that, and only the likes of Amazon can provide that kind of outreach. If it succeeds, the meager profits off the book that Amazon will skim in the process won't matter. Of course, whether it succeeds or not is a gamble, but it's a reasonable one.