ChatGPT Plus has a list price of $20 per month, but the actual cost can vary...

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 cost can vary between $13 and $27 depending on where you buy it. This happens because of factors like VAT or GST taxes and extra fees from app stores like Apple or Google