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

https://wiki-view.win/index.php/Why_Did_OpenAI_Keep_ChatGPT_Plus_at_$20_Since_February_2023%3F

ChatGPT Plus is listed at $20 per month, but the actual price you pay can range from about $13 to $27. This difference comes from added taxes like VAT or GST and app store fees if you subscribe on iOS or Android