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

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

ChatGPT Plus is listed at $20 per month, but the actual price you pay can range from about $13 to $27. This happens because taxes like VAT or GST and fees from app stores get added on top