ChatGPT Plus has a $20 list price, but what you actually pay can vary from...

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

ChatGPT Plus has a $20 list price, but what you actually pay can vary from about $13 to $27. This difference comes from taxes like VAT or GST and extra fees added by app stores on iOS and Android