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

https://highstylife.com/i-keep-hitting-chatgpt-limits-should-i-start-a-new-thread/

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 extra fees like VAT or GST, and app store charges on iOS and Android