This study explores a platform's promotional strategies for its first-party products when the third-party seller carries identical products, taking into consideration consumers' redemption cost incurred in searching and using the coupons, gift cards, and so forth. We determine how the platform vendor's promotional pricing strategies vary with the market expansion effect, proportion of the price-sensitive consumers, redemption cost, commission rate charged to the third-party seller, and third-party seller's choice of the promotional campaign. We find that the platform vendor will charge a higher regular price during the promotional period if the market expansion effect is weak or the commission rate is low. Further, although the market expansion effect expands the scale of the price-sensitive consumers, the promotional campaign does not always lead to an increase in the demand for the first-party product when the market expansion effect is weak, or the market expansion effect is moderate and the commission rate is high. When the third-party seller's promotional decision is given, the platform's promotional campaign is more likely to benefit both the platform and the third-party seller as the redemption cost becomes lower or the market expansion effect gets stronger. Finally, after endogenizing the third-party seller's promotional decision, as the market expansion effect intensifies, the outcome that only one player (the platform or the third-party seller) adopts the promotional strategy is more likely to occur as an equilibrium.

本研究探讨了当第三方卖家携带相同产品时平台对其第一方产品的促销策略，同时考虑了消费者在搜索和使用优惠券、礼品卡等方面产生的兑换成本。我们确定平台供应商的促销定价策略如何随着市场扩张效果、价格敏感消费者的比例、赎回成本、向第三方卖家收取的佣金率以及第三方卖家对促销活动的选择而变化。我们发现，如果市场扩张效应较弱或佣金率较低，平台商会在促销期间收取较高的正常价格。此外，虽然市场扩张效应扩大了对价格敏感的消费者的规模，当市场扩张效应较弱或市场扩张效应适中且佣金率较高时，促销活动并不总是导致对第一方产品的需求增加。当第三方卖家的促销决策给出时，平台的促销活动更有可能使平台和第三方卖家受益，因为赎回成本变低或市场扩张效应变强。最后，将第三方卖家的促销决策内生化后，随着市场扩张效应的加剧，只有一个玩家（平台或第三方卖家）采用促销策略的结果更可能作为均衡发生。