When you purchase an Item in Rise of Firstborn through Google (Android), it is processed using your local currency of the Store region that you are using, but for Apple (iOS), the transaction is processed in USD (Apple’s local currency).
Therefore, iOS purchases made from the US will be based on the prices shown within the game, but there may be applied conversion rates and fees so the actual transaction value may slightly differ from the price in-game if purchasing from countries other than the US.
Also, Google (Android) purchases may also be subject to slight difference in shown price vs. actual transaction amount depending on the region of the Play Store where you made the purchase from, due to conversion rates and/or fees.