ChatGPT Plus lists for $20, but the actual price often ranges from $13 to $27....

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

ChatGPT Plus lists for $20, but the actual price often ranges from $13 to $27. This difference comes from factors like taxes (VAT or GST) and fees added by app stores on iOS and Android