> Books and publishing industries are a result of a technology: paper, printing, binding. Now in the digital age an ebook should cost close the the amount the author get 1$-2$/book.

This is a very technocratic view of book publishing. I think you're leaving out a lot of what goes into creating, marketing and distributing a book which is not labour of the author. Even in the digital age.

Sure, authors could contract those services out using their (expected) revenue on a book. But at some point you'll inevitably get companies offering to manage that process for authors because it creates overhead that distracts from the creative process or thought process: Publishers.

There are lean alternatives to big publishers out there, so it's easy to get self-published. But the weight a big publisher can put behind a release, the distribution network they have, can - even in the internet era - still affect a book's success heavily.