If you plan on making your app cost money you cannot just slab a price on it and hope it sells. Android app marketing can help you determine how high to set your price.
Are there in app purchases? If yes then you may want to keep the price low like $.99, unless you don’t expect many people to buy the in-app purchases that are available then you may want to consider a two or three dollar app.
There are some cases where you may want to set the price of your app for $5, $10, or even $20.Having an app cost this much depends on the life time of the app for each person that buys it. If this app can last someone months at a time and there are little to no in-app purchases then the price can be higher.
If you are not sure how long your app will last you can ask some friends to look at it and ask them how long you think they would have it, and what the price should be. If the app is already released and you think downloads are low try lowering the price enough to get the downloads up while still making money for yourself.
Complete list of Android App Marketing Lessons