-게끔 is a more emphatic version of -게: it marks the result something was deliberately set up to produce. With 만들다 it describes design intent — 그렇게 돈을 쓰게끔 만들어 놓은 거야 (it's built so that you'll spend money), 공기가 이렇게 순환되게끔 만들어 놓고 (built so the air circulates). -게 만들다 says the same thing; -게끔 만들다 stresses that the outcome was aimed at.