When you offer your goods for "auction", it means you are opening the door for pricing.
When you insist on one price that you do not negotiate, write it in the ad.
+ Add to this "Urgent Sale"
A clear word, I want to sell as soon as possible, meaning I will accept the best selling opportunity and that's it. Don't offer goods as if you regret selling them and turn away every customer.
These are basic things most people here have forgotten.