What percentage of those who try to buy an Android inapp purchase end up successfully buying it?

Question

Android

My android app has an inapp purchase (pro version $4). The problem is that according to statistics out of 30 attempts to make this purchase, only 1 succeed. I want to understand if this is a normal statistic, or perhaps something is wrong with the inapp billing code? At the same time, the purchase is successful for me and my friends.