ChatGPT Plus has a list price of $20, but the actual cost you pay often ranges...

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

ChatGPT Plus has a list price of $20, but the actual cost you pay often ranges from $13 to $27. This difference is mostly due to extra charges like VAT or sales tax, and the app store’s markup when you subscribe on iOS or Android