This doesn't make any sense. It's not zero-cost for a company that provides a book to also provide an audiobook. Both require their own supply and value chains.

This doesn't make any sense. It's not zero-cost for a company that provides a book to also provide an audiobook. Both require their own supply and value chains. An audiobook will require recording studios, artists, a streaming audio product, an app, massive storage requirements, separate catalogues and search. The only aspect it shares with the book supply chain (which is also costly for the company) is the IP. It might make sense for Amazon to bundle the kindle/audible versions from a sales POV, but you have no moral right to owning a story in all formats- there are real costs and people involved.