The ChatGPT Plus subscription lists a $20 price, but the actual cost can range...
https://domgodwinson38.gumroad.com/p/why-do-reviews-only-mention-the-160-messages-cap-and-not-the-reasoning-cap
The ChatGPT Plus subscription lists a $20 price, but the actual cost can range from about $13 to $27 depending on where you buy it