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

https://dibz.me/blog/is-there-a-chatgpt-plus-free-trial-i-can-click-to-start-1223

ChatGPT Plus is listed at $20 per month, but the actual price you pay often varies between $13 and $27. Differences come from taxes like VAT or GST and app store fees on iOS and Android