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

https://rapid-wiki.win/index.php/ChatGPT_Plus_Projects_Limit:_How_Many_Files_Can_You_Actually_Upload_Per_Project%3F

The listed ChatGPT Plus price is $20 per month, but the actual charge can vary from about $13 to $27 depending on where you subscribe. This happens because taxes like VAT or GST and extra fees added by app stores affect the final cost