Abstract: Due to the inevitable search cost, there is a Diamond Paradox in the offline market. Intuitively speaking, the online platform market has reduced search costs to zero, so the opposite of Diamond Paradox, i.e., the Anti-Diamond Paradox phenomenon, should appear, that is, goods are priced at rock-bottom levels. However, in fact, price dispersion and price reduction pressure exist simultaneously in the online platform market. To explain this phenomenon, this paper presents a formula of price structure faced by consumers. From the perspective of price structure, the price paid by consumers to sellers is not the actual price spent by consumers, which in fact, includes the price of the commodity, the cost of consumers searching for the information of the target goods and the cost of eliminating the noise of the commodity information collected. The online platform market only reduces the cost of consumers searching for targeted commodity information, but does not actively reduce the cost of consumers eliminating the noise of collected commodity information. On the contrary, it may even increase the cost. This paper proves that the platform does have the power to increase the cost of eliminating the noise of commodity information collected by consumers, puts forward the pricing formula of online merchants based on the price structure, and explains platform and merchants’ online pricing logic, which involves using big data to take advantage of frequenters.

Key words: Anti-Diamond Paradox, price structure, search cost, information noise, pricing