The Asus gpu would be costlier with better cooler/performance but I understand the point that the link belong to the card from same family (so a relative price comparison), Though I understand if OP gets upset trying to justify selling price. But the way he said was rude and unprofessional which is not acceptable at all. A polite reply like "Quoting the post with link : Thanks for the reference but my card perform much better with premium cooling, Though I am open to suggestions if there is a link of same or better card for less than offered price"
Op could have made a point without being rude and other potential buyers will get reference price check from the link, Now if I was a buyer I would keep my distance seeing his reply as if something goes wrong in future I will have to deal with him and its not pleasant.