Return on investment depends on both the return and investment. Once a civ hits Type 1 or Type 2, what they would consider an "expensive" investment is very dif

Return on investment depends on both the return and investment. Once a civ hits Type 1 or Type 2, what they would consider an "expensive" investment is very different from what we would today. To a sufficiently advanced civ, destroying planets would be no more expensive than setting a sentry turret or an automated Predator drone.