To accelerate buyers and seller finding each other and the right deal.
Both buyer and seller when going online and advertising or searching a product (their flat, car etc.) will specify not just one price, but 3 prices. The advertised price, the lowest price they might accept, and a price between these two representing what they really would consider an immediate deal price. The system (machine or human) will try and match buyer and seller based on these 3 parameters.