Presents a cost estimation method based on function characteristics and the technique of quality function deployment (QFD). Based on the cost structure, the total costs of some well-known competitive products of the developed system are then investigated. The function levels of these well-known products are identified one by one by means of the QFD technique. By integrating the information about the competitor's costs and the function levels, a set of cost factors which are used to evaluate the system costs is derived by using the least-square-method. As a result, the total cost of the designed system can be estimated quickly through simple steps of calculation. Furthermore, the successful probability of a system being designed within someone budget can be assessed in advance.