He hasn't really achieved a very prominent position in the mac app store though. The post there shows he is 6 in the 'developer tools' category. I suspect this is one of the least used / lowest sales of any of the sub-categories. Most developers probably aren't looking in the app store for their tools, they already have them, and even if they are, developers make up a small percentage of mac users. Perhaps, only 1% of all mac owners are potential customers... Even less really because they must be mobile developers to make use of his application.

His sales vs position has nothing to do with the appStore and everything to do with being in an extremely tiny niche market.