Sales rankings for chess books? Are there any estimates sales rankings for chess books? How much do a bestselling chess book generally sell?
Obviously, how much money book selling is a business secret. Nobody will tell you, you will never get the information.

But I do work with book publishers, they can comfortably pay my invoices with good profit margin. Furthermore I sell few database apps on the app store (www.smallchess.com), while I'm not a publisher I make non-trivial returns.

Selling chess books won't be make another Jeff Bezos, however, it's still a profitable business. In fact, selling books give better returns than being a 2700+ grandmaster. Unless you're like in the top 20 of the world, selling a good book (or running a business) makes more money.

Why? While the chess marker is much smaller than say football, the chess market is dominated by high-income earners. Chess books buyers have good purchasing power, because if they don't they would have better things to do than chess.

Well known book writers rely on commissions from their books for living.