This paper tries to illustrate by examples that intermediated contractual arrangments make efficiency gains under price mechanisms. There examples of pure exchange environments, one in partial equilibrium and two in general equilibrium, are provided. When asymmetric information causes adverse selection problems, intermediated contractual arrangements with state-contingent payments and randomized information-processing make efficiency gains. Moreover, in some of these examples, intermediated contractual arrangements can be decentralized and coordinate with competitive market prices of goods. A policy implication is that the presence of imperfect information does not necessarily gives reasons for the government's intervention in the market. The market itself can handle information problems. When an appropriate information technology presents in some environments with adverse selection problems, market mechanisms together with intermediated contractual arrangements perform well just as they do in the perfect information world. However, market mechanisms sometimes does not work well enough to eliminate all adverse selection problems. In numerical example 3, we show a case in which contractual arrangements through decentralized intermediaries alone can solve the problem; however, such arrangements cannot coordinate with market prices of goods.