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

https://highstylife.com/i-keep-hitting-chatgpt-limits-should-i-start-a-new-thread/

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