Not everything needs to be done through a traditional publisher of course. Writers might want to keep their ebook rights and act as their very own publisher. Usually in this scenario you'd convert your work into the epub file format (increasingly accepted as the 'normal' format), for instance, then deal directly with on-line sellers to allow it to be accessible for sale. It's not impossible for an individual writer to enter others, who offer conditions on their websites for only this function and an immediate deal with Amazon.
Additionally it is possible to deal directly as a writer with committed on-line digital publishers, like Smashwords (though generally these also will make use of the professional services of the internet giants for doling out their names). Digital publishers offer more control over the procedures of 'make ready' for ebook distribution, along with possibly greater remuneration to the writer. Some are extremely intelligent and creative companies, but writers should take care when they provide digital rights management (DRM)-free ebooks to such publishers; without 'locks', the ebook or samples of it is not going to be protected from misappropriation. Recall, copyright is the writer's main right and protection.
That will mean $4 to the writer. But at this speed, it is still not a terrible outcome. 60% with 25% of that to the writer, to the publisher, means 15% of the $20, or $3.