Merchandizing, which also involves exploiting labor and investments, which involve exploiting the market. Also, it’s not like she personally sold the books, low-wage bookstore employees sold them while she promoted them. Anyway, she would have pulled 10% on the net profit, probably a little more over time, and the total book sales in USD are ~$7.7 billion. So let’s say that’s entirely profit (it’s not), that’s $770 million as of 2017. She allegedly made her first billion in 2005. It literally couldn’t have been from book sales.