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

https://sierra-wiki.win/index.php/Why_Does_ChatGPT_Plus_Cost_More_Than_$20_for_Me%3F

ChatGPT Plus has a listed price of $20 per month, but the actual amount you pay can range from about $13 to $27. This variation happens because of things like taxes (VAT or GST) and extra fees added by app stores such as Apple’s or Google’s