Beyond the cost aspect that other commenters have referred to, they're evolving tech. They're the first ones to have a working full-flow staged combustion cycle rocket engine (the Raptor, currently used in the Starship prototypes), something the Soviets tried before and failed. Their Dragon capsule was also a gigantic technological leap relative to the admittedly tried-and-true Soyuz, and it also looks far more comfortable for astronauts than the Soyuz does.