How much money does a fiction writer earn?

It depends on how many books they can sell. Some of the money from the books goes to the publishers and printers.
That is right, but first of all getting into the industry is hard. the writing industry is very competitive, and getting your manuscript in is tough enough, especially for fiction.
but the main basis is, if your a great writer, if no one looks at your book then you got peanuts, people say don't judge a book buy its cover, but really, that's a lie.
a writer who isn't very well aknowleged (which is about 9/10) earns very little.
a best seller earns....well...it depends, from millions, to a ok price.
I wouldn't pay attention to the last response as it is both factually wrong, and contains numerous grammar and spelling errors. An author's pay is based on so many variables. But most always consists of the money they are paid upfront, and the percentage they receive from each book sold. This percentage varies. If this is your first book then don't expect much. Keep this in mind, even though publishers only print the best stories, just because one publisher turns your book down does not mean it's bad. It may just be it doesn't fit the criteria of what they usually print. Keep on writing!