There are two types of NFT auctions on OpenSea, The Dutch Auction, and the English Auction.
With the Dutch auction, the price of the NFT being sold will decrease until somebody buys the NFT. The Dutch method is risky as you can end up selling your NFT for less than you bought it.
Therefore, most sellers use the English auction for their NFT sales.
OpenSea English Style Auction
First, when setting up an NFT auction for sale to the highest bidder, it is essential to add a minimum reserve price. This ensures that you don’t end up selling your digital asset for a paltry sum if your reserve price isn’t met.
Once, you set your reserve price you leave the sale up to market forces.
On OpenSea the minimum reserve must be no lower than 1 Ethereum as OpenSea will cover the transaction fee if the auction ends in a sale. Please note, you can manually accept a bid below your auction price at any time, but you will need to pay the transaction fee.
NFT sales price not met
If the price you set for your NFT is not met within the time limits of the auction no sale will occur. The owner can either create a new auction or sell the NFT via one of the other methods.