ChatGPT Plus lists at $20 per month but the real cost often ranges from $13 to...

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

ChatGPT Plus lists at $20 per month but the real cost often ranges from $13 to $27 depending on where you subscribe. This difference comes from extra fees like VAT or GST taxes and app store markups on iOS and Android