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

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

ChatGPT Plus is advertised at $20 per month, but the actual price can range from about $13 to $27 depending on where you subscribe. This difference comes mainly from taxes like VAT or GST, and extra fees from app stores like Apple or Google