Your purchase cost total always appears on the screen prior to the conclusion of the transaction and is indicated on the receipt sent by your app store to your email address. In some countries/regions the total purchase cost includes taxes that depend on the country indicated in your app store account.

Note: When making purchases through the App Store, your payment method is charged at the time of purchase or within a few days.

Several purchases can be bundled into one transaction and reflected on a single receipt. The receipt might also take several days to be sent to you, which is why you might get the impression that all the purchases on a receipt were made on the day you got it.
If it is unclear what purchases are reflected in the receipts, please review your purchase history and check whether a few orders were not bundled together as a single payment.

If there are still questions remaining regarding your purchase total, please contact your app store's support team. They can help you clarify the purpose of any additional payments and the peculiarities of taxation in your region.