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

https://web-wiki.win/index.php/Why_Does_ChatGPT_Plus_Cost_More_Than_$20_for_Me%3F

ChatGPT Plus is listed at $20 per month, but the actual price you pay can range from about $13 to $27 depending on where you subscribe. This happens because of factors like local taxes such as VAT or GST and extra fees added by app stores