If you read the article, he did mention that his wife wasn't very happy that the server was taking 20-30% of the app's revenue. Then later on in the article he

If you read the article, he did mention that his wife wasn't very happy that the server was taking 20-30% of the app's revenue. Then later on in the article he mentioned that he took the server cost from an average of $10 a day to just the free tier. Based on this information I deduced that the revenue hovers around ~$1,000 a month? Not sure if this rough calculation is accurate though.