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

https://wiki-wire.win/index.php/What_Is_the_Max_File_Size_for_ChatGPT_Plus_Uploads%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