ChatGPT Plus has a list price of $20 per month, but the actual amount you pay...

https://smoothdecorator.com/why-did-openai-keep-chatgpt-plus-at-20-since-february-2023/

ChatGPT Plus has a list price of $20 per month, but the actual amount you pay can range from about $13 to $27. This difference is due to factors like local taxes such as VAT or GST and extra fees charged by app stores for iOS and Android