The main idea behind this simplification is that supply and demand adjust during a preliminary phase until equibrium prices are reached. Transactions that clear the market are then performed in some unexplained way. In these, buyers sample sellers according to some rule and buy from the cheapest.
All sellers are anonymous and are searched with equal probability.
Such models seem to be plausible for transactions which take place infrequently and where the gain in information obtained by searching makes such searching worthwhile. This is the case, for example, when an individual purchases a car or a firm purchases an expensive piece of equipment. Yet many other markets are ones on which individuals trade frequently for relatively inexpensive goods. On such markets it seems to make intuitive sense to profit from the experience gained from previous transactions to select a supplier and this may lead to the establishment of preferential links between buyers and sellers. Of particular interest is the case of markets for perishable goods.