Puzzle Breakers is a free-to-play game that may offer additional in-app purchases for players who want to slightly increase the game pace. Please note that purchases do not have any effect on chances of receiving loot, etc.
In-app purchases that are made with real money are clearly stated as such with actual monetary values.
You can amend in-app purchases settings via your mobile device settings by following these instructions:
Android
Google Android device in-app settings
iOS
Prevent in-app purchases from the App Store