I wouldn't be so sure. Programming has a distinct advantage: people can make money from programming skills. And also, people can save money on programming costs

I wouldn't be so sure. Programming has a distinct advantage: people can make money from programming skills. And also, people can save money on programming costs if a book teaches them/their programmer enough knowledge that outside talent isn't required. So there's a lot more money potential for the average programming book than there is for the average novel. (Bestselling novels make much more, but only a few books get that status)