The control of the costs, as soon as possible of the product life cycle, became a major asset in the competitiveness of the companies confronted with the universalization of competition. After having proposed the problems related this control difficulties, we will present an approach defining a concept of cost entity related to the activities of the product to be designed and realized. We will then try to apply this approach to the fields of the sand casting. This work will highlight the hierarchisation difficulties with the entities composing the models created as well as the limits of a generic approach.