It's the great American dream to write a novel or a biography or a history book or a children’s book or a.... well you get the idea.
People will pay just about any price if you can make their dreams come true, but without them having to do any of the hard work.
Everyone wants to write that great novel, but people lose interest quickly. If you can come up with a product idea that either motivates them daily to get their book written or can somehow write the book for them with some sort of software or I don't know how, you will make a fortune.
In the mean time however, you can capitalize on this craze by writing a few short guides on all different aspects of writing.