The listed price for ChatGPT Plus is $20 per month, but the actual charge can...

https://wiki-velo.win/index.php/Is_ChatGPT_Plus_Cheaper_on_the_App_Store_in_Italy%3F

The listed price for ChatGPT Plus is $20 per month, but the actual charge can vary between $13 and $27 depending on where you subscribe. This happens because of extra fees like VAT or GST in some countries, or app store markups on iOS and Android