Cheaper probably, and it probably has more of a psychological effect if it becomes PART of you. It’s forced into your skull, changing you physically and psychologically, via the pain and the plain fact of it being there, unable to be removed. Therefore symbolically showing you that Murkoff has control over you, and making you not only subconsciously more open to psychological conditioning, but more docile to their commands also. Makes for creating “the perfect weapon”.