Source: http://priceonomics.com/can-authors-make...

A 2012 survey, appropriately titled Not a Gold Rush, gives us perhaps the best insight into the economics of self-publishing. Over 1,000 self-published authors were questioned and the results were sobering. The average self-published author earns $10,000 a year. And even that meager sum is skewed by the more popular stars of the self-publishing economy. 10% of the authors in the study made 75% of the money. 75% of authors made under $500.