ChatGPT Plus has a listed price of $20 but the actual cost you pay can vary...

https://www.cool-bookmarks.win/chatgpt-plus-is-officially-listed-at-20-per-month-but-the-actual-cost-often

ChatGPT Plus has a listed price of $20 but the actual cost you pay can vary between $13 and $27. This difference comes from taxes like VAT or GST and extra fees added by app stores on iOS and Android