The difference is that Boeing and others are financed the way a public works would be, like a bridge or highway. They thus have no incentive to get cheaper / more efficient once they get the contract, and in fact make more money the less efficient they are -- as long as the government doesn't tire of paying them. SpaceX gets development subsidies, like the others do, but they sell launches, not an ongoing project. As a result, the more efficient they are, the more profit they make.

United Launch Alliance (ULA), sells launches. ULA sells launches for Delta IV Heavy and Atlas V. ULA is Boeing/Lockheed joint venture.

Mars Reconnaissance Orbiter, New Horizons, Starliner crew capsule ... basically all NASA and DoD launches come from ULA.