NASA boasts that its Space Launch System (SLS) is the most powerful rocket it has ever built, but those following the twist and turns in the endless saga know it's likely also the most expensive. The agency contracted with Aerojet to built 24 engines at $146 million a piece. Every expendable SLS rocket will be outfitted with 4 engines; that's $584 million for the engines alone. This does not include the cost of manufacturing the launch vehicle's massive core stage, solid-rocket boosters, upper stage, and other associated expenses. Add it all up and the launch of each SLS rocket is expected to come in at a whopping $2 billion dollars.
For the price of just a single SLS $146 million engine, NASA could purchase six RD-180 engines from Russia, two Atlas V rocket launches, three "flight-proven" Falcon 9 launches, or a Falcon Heavy launch. Why does NASA insist on overpaying for SLS? According to NASA’s own website, "Men and women in all 50 states are hard at work building NASA's Deep Space Exploration Systems to support missions to the Moon, Mars, and beyond." So there you have it.