I bought Minecraft PE a few months back but the tablet that I bought it on broke and I had to get a new one. Just recently, when I went to go download the game again I saw that I had to pay $6.99 for it. I made sure to be on the same Google account that I had bought it on previously, but even then it still showed me that I had to purchase it. Is there anyway to avoid paying again?
The fact that the price is being shown may most likely be a bug. App purchases through Google Play are tied to your Google account, therefore you should still be able to obtain Minecraft: Pocket Edition on another Android device wtihout paying anything extra (provided that you're using the same account).
Source: personal experience with using Android, plus this Android StackExchange answer.