In the last decades, planning of chemical plants was the topic of several investigations. Optimization of individual process units was also an important topic in chemical engineering research and practice. The results of these optimizations have led to significant improvements in process design. In the plant lifecycle bid preparation is another important point in plant design. Much research work on cost estimation has been done 25 or more years ago. The quality of the bid has a great influence on the economic success of the company. Therefore, bid preparation must have an important place in the planning process. The use of optimization programs with modem methods of rigorous simulation and computer aided engineering tools could led to significant improvements in the bid preparation process. Nevertheless a qualified and meaningful cost model is still very important for this process. The overall results are a better plant design and an exact estimation of the investment and operating costs. Thus, this approach could help to increase the efficiency and the cost accuracy of about 90% of the real investment and operating cost.