Peoples' sense of value is all out of whack IMO, that's an amazing deal for something that looks like it can be a real, serious sketching/drawing tool. FIFTEEN DOLLARS!! That really does not seem like a great hardship for someone who can already afford a $500-$800 iPad and $10-$30 stylus. A few years ago, you couldn't even get a piece of shareware utility software that makes animated .gifs for $15, now you get a mini art studio, sheesh.
True, but that is the state of the competition these days. Nickel and diming your users for every brush is not going to go over well.