Let us analyse the product life cycle and the impact of decisions in term of generated costs. The early phase of design implies between 70 and 85% of the product cost and, at the end of the detailed design the margin on the final cost is thus very limited (cf. Fig 1). Contrary, the evolution of the costs really engaged by the company are very limited in these upstream phases. However, it is there that the control of the costs should be really exerted.