@Denisovrocks So here is my question back to you: How complex was the app? How many hours did you pour into it? Imho, $/h is a lot more interesting! Sure, there are people who sit down for an hour and present the finished app, then get paid several thousand $$$, but that only happens to the least of us...
As for me, I think that you can charge $30+/h easily if you are a student and just started out with Android development (you should, however, already be able to create apps and have a good understanding of programming)
The more you do, the better you become, the faster you become, the more you can charge!