ChatGPT Plus has a listed price of $20 but the actual cost you pay can vary...

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

ChatGPT Plus has a listed price of $20 but the actual cost you pay can vary between $13 and $27. This difference comes from taxes like VAT or GST and extra fees added by app stores on iOS and Android