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

https://www.slideserve.com/aaron_ward92/why-does-chatgpt-plus-cost-more-on-android-than-on-the-web

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