Intercepting and destroying projectiles in midair is costly business. Rockets, like the Qassams and Katyushasfired into Israel by Hezbollah and Hamas, cost around $1,000 each. The counter-missiles that theIron Dome, Israel's rocket defense system, uses to destroy incoming rockets are far more expensive: about$40,000 a pop. This disparity, and the accompanying prioritization of what gets defended, means the Iron Dome ignoresanything smaller thanrockets and artillery shells.