As usual, one cannot post anything money related on a startup oriented forum apparently.
I would hope if a person is selling something there's a material improvement over free offerings--even if that's as minor as a unique voice, audience, or presentation. For example, the parent link is a series of static html pages with Javascript examples, while this post is a video series with compiled examples using SDL with extras like a discussion forum. I can see a good reason to pay money for that, but I can also see the appeal of the free alternative depending on your goals.