Why Should cost modeling in required while taking Purchasing Decision ?

We have to do cost modeling before purchasing because after cost modeling we easily analys that how much discount and best price & services getting from which supplier. And which supplier are best and famous in same item.

COST MODELING IS DEEP ANALYSIS OF MARKET AND BECAUSE OF THAT WE CAN GET IDEA ABOUT TODAYS MARKET SITUATION, POWER OF NEGOTIATION, NUMBER OF SUPPLIERS AND THE ACTUAL TENTATIVE VALUE OF MATERIAL. SO COST MODELING IS REQUIRED WHILE TAKING PURCHASING DECISION.