Here are the economics of publishing a typical novel. For the sake of mathematical cleanliness, let's assume a first print run of 10,000 copies, an advance of $10,000, and a price tag of $20.

10,000 x $20 does not add up to $200,000. The average discount to bookstores, libraries, etc is 48%, which means that if the whole run sells out, the publisher gets $104,000. Almost never does the whole run sell out. If the author is lucky, 7500 copies will sell - a "75% sellthrough," a very good percentage. (50% is more typical.) This means that the publisher actually gets 75% of that $104,000, or $78,000.

From this money must be deducted direct expenses for production . . .

Nice set of data on the costs and potential revenue of writing a book . . .