I've also heard that fuel is not the main cost contributor to a rocket launch. In fact, it is a really insignificant portion of the cost. It is the vessel that

I've also heard that fuel is not the main cost contributor to a rocket launch. In fact, it is a really insignificant portion of the cost. It is the vessel that contains giant amounts of fuel that is costly. Hence reusability from SpaceX makes sense and so does launching the rocket from high altitude to avoid building the first stage all together.