Choosing reasonable pricing strategies has become key for platform enterprises to maximize profits. A platform supply chain consisting of a manufacturing platform, a manufacturer, and an offline retailer is considered. A noncooperative-cooperative biform game is constructed to discuss the pricing competition and profit-sharing among the platform supply chain’s members. In the noncooperative game part, the wholesale price of the manufacturing platform and the retail prices of the manufacturing platform, manufacturer, and offline retailer are chosen arbitrarily as strategies. In the cooperative game part, the manufacturing platform and offline retailer share showrooming profits to form a cooperative coalition. They optimize the profit-sharing ratio and service level to maximize the coalition’s profit. The Shapley value is used to distribute the coalition’s profit. A numerical example is used to analyze the effects of online channel preference, manufacturer product recognition, and service cost coefficient on Nash equilibrium strategies, the optimal profits, consumer surplus, and social welfare. Some findings are as follows: Under price competition, cooperation between the manufacturing platform and offline retailer is effective in improving the service level and their profits. When online channel preference increases, maintaining stable sales of offline channel can help the manufacturing platform cope with the competition among alternative products. A tripartite win-win can be achieved among the manufacturing platform, offline retailer, and consumers, leading to improved social welfare.