Project consultants way of estimating the cost

The project consultants/ detailed engineering contractors are selected by the owners setting up the plant based on the detailed engineering companies experience in their previous projects, the resources that company have to execute the project and their collaborators who can extend their support during execution of the project including the technical knowhow the project consultant they have of their own or with tie up with their collaborators. Even though the detailed Engineering consultant posses major above said qualities the cost element plays a vital role while selecting the project consultant by the owner. Hence it becomes very much necessary for the project consultant also to optimise their cost to secure the contract with the owner. In normal circumstances all the companies wants to save the cost of the project from day one which will help in completion of the project within the budgeted cost. .The owner starts control process  with floating of tenders to various project/detailed engineering consultants . The project consultants/ detailed engineering contractors starts working in their estimate  with basic inputs provided by the owner and develop the mass flow/ heat flow diagrams. The basic main important equipment details  are provided by owner or by the process licenciator. On development of the said drawings the detailed engineering contractors calculate the number of drawings which may be required to be designed and detailed by them during the execution of the project. The number of P&I diagrams required, the number of isometrics to be designed etc are calculated by the companies. If the owner further wants the contractor to carry out other services like monitoring of supply of equipments, supervision of civil, mechanical, electrical & instrumentation works .The consulting companies start calculating the man-hours required to be spend by the company for developing whole project drawings and number of man hours going to be spent on other activities. Based on market rates of Engineers/technicians and other category personals required  for that project the total cost of the consultants are calculated. In case of any tie up required from partners of other nations  the cost of that is also included. Finally considering the overheads and profit margin that particular company maintains are included to arrive at the final quotation cost by the project consultants