The economics of remanufacturing depends on the quantity of products returns and on the demand for products. Under the assumptions that price of product collection affects collection rate, the maximized cost-savings and the corresponding optimal price and rate were analyzed by constructing the product sales curves and recovery curves with limited life cycle. Research results show that: 1) given the limited market demand and positive correlation between collection price and collection quantity, enterprises who simply pursuit to reduce manufacturing costs may undertake greater cost; 2) the longer time the products flow in the closed-loop supply chain, the lower profits remanufacturing activities will be obtained; 3) products which have a good customer basis and can gain consumers recognition quickly has more advantages in remanufacturing activities. These conclusions provide a theoretical and method support for the enterprise remanufacturing activities in real business.