High-energy lasers are increasingly viewed as the most cost-effective way to defend against drones and missiles launched by Iran at oil refineries and US bases across the Middle East. Shooting a laser is cheap — as little as $3.50 a shot, according to some estimates — compared with systems, like Patriot missile interceptors, that can cost more than $3 million per shot to neutralize a drone.President Donald Trump told reporters this week that lasers would soon be able to do the work of Patriot missile interceptors “at a lot less cost.”