The store often undersold items to attract customers, even at a loss.

undersold 是动词 undersell 的过去式。undersell 由前缀 under-（表示"低于"）和动词 sell（出售）组成，字面意思是"以低于...的价格出售"。在商业中特指"以低于成本价或市场价出售"。