This kind of story always reads like a financial fail. He should pay himself a normal programmers salary (something around 50k/year for a beginner might be fine, also he is not a beginner, because he knows a lot about presentation and UX design) and THEN calculate his profits. Probably this App is way in the minus.
Also you must consider that he just has around 1k customers and all of them on the same plattform. Also these customers only paid him once and not regularily. That are 4 big risks: low number of customers, no guaranty to get any dollar next month and a high dependence on one plattform and high dependence on the success of this one app.
Another risk, I nearly forgot about, is that the core feature of his app, the speach engine, is not even his own. What if Acapela decides they make their own App in this direction.
Concluding everything I think he has a low income, unprofitable, high risk business. Not the position I want to be in, when I quit my dayjob.
edit I just now see that you posted the link yourself, Nathan. Please read all "he"s as "you". ;-)