The purpose of this chapter is to review the main advantages claimed to arise from arms collaboration. The discussion is theoretical in nature, particularly with regard to the arguments advanced for cost savings. Here, the focus is to explain in simple terms why arms collaboration and therefrom standardisation provokes such a rallying call when approached from an economic standpoint. The chapter details the primary sources of cost savings, illustrating the benefits to be obtained from trade, scale, learning effects, and non-duplication of R&D. The comparison between theory and practice is then briefly explored to determine the importance of collaborative cost savings in reality. The chapter closes with a summary discussion of the benefits collaboration is purported to confer on military efficiency.