The listed ChatGPT Plus price is $20 per month, but the actual charge can vary...

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

The listed ChatGPT Plus price is $20 per month, but the actual charge can vary from about $13 to $27 depending on where you subscribe. This happens because taxes like VAT or GST and extra fees added by app stores affect the final cost