I think the author's point is that it doesn't matter if he convinced you that the app itself was worthwhile; paid app development is not a tenable model for a solo developer. App prices are too low, competition is too high, and getting the word out to customers is difficult and expensive.
Let's say he was simply much better at convincing people and had twice as many people purchase the app as he did. He still would only have made $50,000 from a year of working 60 hour days; and the majority of that revenue came in the days after release while it was still "new" and receiving lots of free press attention (and is not likely to repeat itself in the absence of a marketing campaign).
Keep in mind he now has to support the people who purchased his app while delivering improvements to a new version. Since you likely converted a large chunk of the people who would be interested in your app during your launch free publicity phase, there's a smaller pool of potential customers out there. You can either spend money on building features for users who will never pay you again, or you can spend money on marketing.
Moral of the story here is that the success of a product usually has very little to do with the merits of the product itself and much more to do with marketing. Marketing isn't something you can DIY; it costs money and if you're selling a niche $5 app, you're probably not going to see much return from a marketing campaign either. Without significant marketing or winning the viral popularity lottery, you're probably not even going to make minimum wage off the time you put into your app. The author is just opening his books so other people know what they're getting into.
Let's say he was simply much better at convincing people and had twice as many people purchase the app as he did. He still would only have made $50,000 from a year of working 60 hour days; and the majority of that revenue came in the days after release while it was still "new" and receiving lots of free press attention (and is not likely to repeat itself in the absence of a marketing campaign).
Keep in mind he now has to support the people who purchased his app while delivering improvements to a new version. Since you likely converted a large chunk of the people who would be interested in your app during your launch free publicity phase, there's a smaller pool of potential customers out there. You can either spend money on building features for users who will never pay you again, or you can spend money on marketing.
Moral of the story here is that the success of a product usually has very little to do with the merits of the product itself and much more to do with marketing. Marketing isn't something you can DIY; it costs money and if you're selling a niche $5 app, you're probably not going to see much return from a marketing campaign either. Without significant marketing or winning the viral popularity lottery, you're probably not even going to make minimum wage off the time you put into your app. The author is just opening his books so other people know what they're getting into.