We analyze a systematic relationship between transaction mechanisms and wholesale pricing schemes within a supply-chain with two competing suppliers and a monopolistic retailor. When one of the suppliers changes its transaction mechanism from an independent scheme to a cooperative one, then the wholesale prices of the suppliers become cheaper than before. When one supplier changes its transaction scheme to a cooperative one while the other supplier sticks to the existing independent transaction scheme, we show that the supplier with a cooperative transaction scheme can realize the increased profit via a profit sharing contract with the retailer but the supplier with independent transaction scheme can face the decreased profit. We also show that both suppliers can achieve the higher profits by adopting the cooperative schemes with the retailer.