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

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

ChatGPT Plus is listed at $20 monthly, but the actual price you pay can vary between $13 and $27. Differences come from taxes like VAT or GST and extra fees from app stores on iOS and Android