A bid-ask resale marketplace is a resale marketplace that sets prices the way a stock exchange does. Buyers post bids, the prices they are willing to pay. Sellers post asks, the prices they are willing to accept. A sale happens automatically when a bid and an ask meet. The marketplace then checks that the item is genuine before it reaches the buyer. This model is used mainly in America, for sneakers, streetwear, trading cards and other collectibles, so the example on this page is set there, in US dollars.
On an ordinary resale site, each seller sets a price, and buyers accept it or move on. That suits one-off items, such as a used sofa. It works less well for items that are identical, such as a new, unworn pair of one sneaker model in one size. Hundreds of people may want to buy or sell exactly that pair. For identical items, a market of bids and asks shows the current price at a glance.
Consider one sneaker model, in US size 10, in the United States. Three buyers have bids open: $210, $220 and $225. Three sellers have asks open: $250, $245 and $240. The highest bid is $225 and the lowest ask is $240. No sale happens, because no buyer will pay what any seller wants. The gap of $15 between them is called the spread. Then a new buyer posts a bid of $240. It meets the lowest ask, and the marketplace's software matches the two at once. This is the same job that a matching engine does on a stock exchange, where the page on stock trading and settlement explains it for shares.
The seller does not send the sneakers to the buyer. The seller ships them to the marketplace's authentication centre. There, staff and machines check the box, the stitching, the materials and the smell of the glue, as described in product authentication. Some checks use AI microscope authentication. If the pair is genuine and unworn, the marketplace ships it to the buyer and pays the seller $240 minus its fees. If it is fake, the buyer gets a refund and the seller is penalised.
The record of every sale is public. So a buyer can see what the same pair sold for yesterday, last week and last year. That history is the price guide.
How is this different from dynamic pricing? In dynamic pricing, the seller's software changes the price. In a bid-ask market, nobody sets the price. It is wherever the highest bid meets the lowest ask. It is one of the ways in which recommerce works.