If you cooperate with a traditional publisher, the editors will do something necessary to meet their employer's standards and perform their duties. If the structure is unreasonable, this may include the content/development editor "remodeling" the book. But it may not include the revision of the book by the copywriter, unless it is poorly written, unclear or inconsistent.
When I was working in a publishing house, my editing level largely depended on how well this book was written. Some books need more work than others. Almost any level of editing is considered "legal" as long as the goal is to conform to the publisher's style guide and edit 5c. The warnings are "Don't fix things that are not damaged" and "Don't change the author's tone". Within these ranges, we do everything possible to make this book better.
When I hear people talking about editing, they seem to think that the editor wants to control the book and make it his own. Let me be clear: most editors don't want your book to be their own. They want to help the author write better. In order to do this, they often have to struggle with the author's ego or belief, because they know more about grammar/genre conventions/industry standards than editors. Editors make some suggestions because they have written countless other books, and they know what is useful, what sells well and what is not.
If you are self-publishing, editors will accomplish your goals in the way you hire them and the way they think is best for your book. This is why it is important to hire the right editor for your book and the type of editor that suits your needs. This is why you need to know your goals and needs very clearly before working with any editor.
When a self-published author comes to me, I ask a lot of questions to determine what they want and need. It may be an editorial evaluation full of objective feedback and suggestions. It may be a hands-on developmental editor to reshape the structure of the book. This may be a copywriting to make the wording more concise or precise. As long as what the author wants, demands and pays is legal.
Once again, the purpose of editing is to make your book better and help you achieve your goals.
So how much is the author's manuscript fee? This book belongs to the author forever. No matter how much the editor changes, thinks or phrases, it's useless. This book exists because the author wrote it. It wasn't written by the editor. They are just helping the author carve stones into diamonds-or polish rough diamonds into sparkling diamonds.