ChatGPT Plus is listed at $20 per month, but the actual price you pay can vary...

https://research-wiki.win/index.php/Does_ChatGPT_Plus_Include_Advanced_Voice_and_Is_There_a_Cap%3F

ChatGPT Plus is listed at $20 per month, but the actual price you pay can vary between $13 and $27. This difference comes from extra fees like VAT or GST, and additional charges on app stores for iOS or Android