ChatGPT Plus is listed at $20, but the actual price you pay can range from...

https://astro-wiki.win/index.php/Why_Does_ChatGPT_Plus_Cost_More_on_Android_Than_on_the_Web%3F

ChatGPT Plus is listed at $20, but the actual price you pay can range from about $13 to $27. This difference comes from things like VAT or GST taxes in your region and extra fees app stores add on iOS or Android