Due to the influence of globalization, the improvement of technology and the diverse demand of customer and other factors make enterprises co-opetition be crucial. When the enterprises pursue the profit maximum or cost minimum, they must also consider the quality of products. In addition, a variety of production cost in the process can be considered to increase customer purchase intention with proper investment in quality improvement. The purpose of this study is to refer to literature by using single buyer and single seller to represent a simple supply chain. The cost model can be extended to generate the manufacturing process on both sides. The objective is to obtain two decision variables including price and defective quality in order to maximize the profit in a cost-benefit mathematical model. Finally, an example is given to illustrate a cost-benefit model and explain the relevant cost and benefit components of single buyer and single seller in this model. This study can help future researchers develop the value chain in supply chain management.