ChatGPT Plus is listed at $20, but the actual price you pay can be between $13...

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

ChatGPT Plus is listed at $20, but the actual price you pay can be between $13 and $27 depending on where you subscribe. This difference happens because of extra fees like VAT or app store charges