Authors and Self-Publishing

[Point Point]

I went to cafepress and did some math. A 300 page book would cost 16 bucks if sold as a print on demand book. This means that the authors of a close to 300 page book like Professional Nolimit Holdem could make 14 bucks per 30 dollar copy.

My guess is that they probably make 3 bucks per copy being published by two plus two. My question is, why don't the poker authors just self-publish as print on demand on cafepress or lulu? Even if they sell less copies they make much more per copy.