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

https://atomic-wiki.win/index.php/ChatGPT_Plus_Deep_Research_Not_Working:_Did_I_Hit_the_10_Per_Month_Cap%3F

The listed ChatGPT Plus price is $20 per month, but actual costs can vary from $13 to $27. Differences come from factors like taxes (VAT or GST) and extra fees added by app stores