The price of each option (Spotlight or Premium) and its duration are shown clearly in the app, before any payment. You see the exact amount before confirming.
Prices shown in the App Store and Google Play are tax-inclusive: the applicable VAT is already included in the amount you pay.
The VAT breakdown appears on the receipt issued by Apple or Google after the purchase. That document serves as your tax record for the purchase.
Prices may vary by country and by your store account's currency. The amount actually charged is always the one shown on the confirmation screen.