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

https://source-wiki.win/index.php/How_Do_I_Cancel_ChatGPT_Plus_on_Google_Play%3F

ChatGPT Plus is listed at $20 monthly, but the actual price you pay can vary between $13 and $27. Differences come from taxes like VAT or GST and extra fees from app stores on iOS and Android