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

https://wiki-square.win/index.php/What_Is_the_ChatGPT_Deep_Research_Limit_on_Plus%3F

ChatGPT Plus is listed at $20 per month, but the actual price you pay can range from about $13 to $27. This happens because taxes like VAT or GST and fees from app stores get added on top