If you purchase a subscription via our website, you will be charged in US dollars. While the Bear Cave is tucked up here in the Canadian north, we have customers all over the world. Given that, we've had to choose a currency that works internationally and the US dollar is the closest thing we can find to a universal currency.
Sometimes when USD is converted to your local currency it may fluctuate depending on the current exchange rate, so this can mean there's some variation in what you are charged depending on the month or year. This exchange rate is set by your bank and sometimes local taxes or international transaction fees may be added as well.
If you purchase a subscription through one of the mobile app stores (Google Play on Android, the App Store on iOS), this behaviour will differ. The mobile stores base the cost of a subscription off of the worth of your countries currency at the time we last updated our pricing. That means that you may be using a slightly older exchange rate when purchasing through those stores. When purchasing a subscription through one of the app stores, you'll be shown the price in your local currency.