During the negotiation, he showed his hand by revealing his price openly.

showed his hand 是一个习语，其中 show 意思是"展示、显露"，hand 本义是"手"，在这里比喻"手中的牌"。 这个习语源自扑克牌游戏，字面意思是"亮出手中的牌"，引申为"暴露自己的真实意图或底牌"，常用于商业谈判或竞争中表示"公开自己的底线或真实想法"。