You can check the final payment amount on the screen right before payment, and it is also stated in the App Store receipt.
Additional VAT may be charged in some areas.
Your region is automatically determined by the region selected in your App Store profile.

In some cases, a number of purchases are stated together on a single receipt. It may take a few days for the actual receipt to be sent, so you may think that the entire amount stated on the receipt was paid on the same day. If you want to know more about this, please refer to the link below.

Android
Apple

Nevertheless, if you believe that you have been charged more than your actual payment, you can contact your app store for more information on your purchase items and online purchase VAT policies in your area.