ChatGPT Plus has a listed price of $20 per month, but the actual cost you pay...

https://wiki-wire.win/index.php/What_Is_the_Max_File_Size_for_ChatGPT_Plus_Uploads%3F

ChatGPT Plus has a listed price of $20 per month, but the actual cost you pay can vary from about $13 to $27. This difference comes from factors like local taxes (such as VAT or GST) and extra fees added by app stores on iOS and Android