The listed ChatGPT Plus price is $20 per month, but actual costs can vary from...

https://charlie-wiki.win/index.php/ChatGPT_Plus_File_Upload_Limit_Per_Message:_Is_It_10_Files%3F

The listed ChatGPT Plus price is $20 per month, but actual costs can vary from $13 to $27. Differences come from factors like taxes (VAT or GST) and extra fees added by app stores