A single seller offers one or more goods to a single buyer. The buyer's values and the seller's costs are private information. Each player has a commonly known prior over the other player's value or cost, supported on a finite set. What is the optimal selling mechanism? We argue that, despite this question's importance and apparent simplicity, prior work offers no satisfactory answer. If the seller simply chooses an optimal menu given her realized costs, she fails to exploit her informational advantage. At the other extreme, the optimal trade mechanism that satisfies IC/IR constraints for both parties fails in practice, as it conditions prices on the seller's unknown costs in an unenforceable way. The seller's realistic capabilities lie somewhere in between: she may leverage private information but lacks unlimited commitment power. To bridge this gap, we consider a solution concept built on the realistic assumption that the seller can commit to prices but nothing more. Similar -- albeit technically distinct -- solution concepts have been studied in the context of auctions with multiple buyers. Our concept proves surprisingly rich even with a single buyer. In our model, the buyer and seller engage in multiple rounds of cheap talk before the seller posts a menu of priced bundles. The buyer then purchases. We measure value as profit for the seller and consumer surplus for the buyer. We prove that with a single good cheap talk cannot help either party, but show that it creates value in any extension of this canonical setting: multiple goods, multiple units, interdependent values, or repeated play. We also show that multiple rounds of communication can yield strictly higher expected profit than a single round. Finally, we discuss how realistic factors beyond our stripped-down model combine with cheap talk to enhance this value even further.

翻译：单一卖方向单一买方提供一种或多种商品。买方的估值与卖方的成本均为私人信息。双方对对方的价值或成本均持有共同已知的先验信念，且该信念支持于有限集上。最优销售机制是什么？我们认为，尽管该问题具有重要性与表面上的简洁性，现有研究未能提供令人满意的答案。若卖方仅根据其实现成本选择最优菜单，则未能利用自身信息优势。而另一极端，满足双方激励兼容与个体理性约束的最优贸易机制在实践中难以实施，因其以不可执行的方式将价格条件依赖于卖方未知成本。卖方的实际能力介于二者之间：她可以利用私人信息，但缺乏无限承诺能力。为弥合这一差距，我们构建了一个基于现实假设的解概念，即卖方仅能承诺价格，但无法承诺更多。尽管在技术上有所差异，类似解概念已在多买方拍卖情境中被研究。即使仅面对单一买方，该概念也展现出惊人的丰富性。在我们的模型中，买方与卖方在卖方发布定价捆绑菜单前进行多轮廉价谈话，随后买方进行购买。我们以卖方利润衡量价值，以买方消费者剩余衡量价值。我们证明，在单一商品情境下，廉价谈话无法为任何一方带来收益，但表明在该经典设定（多商品、多单位、相互依赖估值或重复博弈）的任何扩展中，它都能创造价值。我们还证明，多轮沟通带来的期望利润严格高于单轮沟通。最后，我们讨论了超越简化模型的现实因素如何与廉价谈话相结合以进一步放大这一价值。