Bilingual Child was supposed to be an experiment. We built it in 6 weeks, working on it nights & weekends.
The app was free to download with one available book, including ten vocabulary words, and two additional books offered as an in-app purchase of $1.99.
For the first two months after releasing it we let it sit. We had never released an iOS application and had little idea what to do to market it. To our surprise, it slowly picked up steam. $5 a day. $10 a day. Then $15 a day.