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

https://www.slideserve.com/aaron_ward92/why-does-chatgpt-plus-cost-more-on-android-than-on-the-web

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