For me, the value of the books is the value they provide to their readers, not the money they provide to the author. We want author to be able to get money because it will incentivize them to write. I don't think it's realistic to think any writer will not write because his work may become famous only after he has published some books and therefore won't be as profitable as some other copyright scenario. That is just not how people think.
I know that some people see copyright as some kind of justice system to ensure creators get their due. I think that view in general leads to copyright maximalism, and is not a good place to start from when discussing the value of copyright