The premium currency was introduced to allow players who enjoy my mod but don't want ads or custom items in their game the ability to pay $0.99 for it without having too much impact on gameplay. As more features are added I may introduce additional paid content, but hopefully that won't be necessary.
You can only get the premium currency through in-app purchase on Android. If you try to get it on iOS, you will instead be prompted to support me by donating through PayPal or Patreon if you'd like to help my mod continue running.