For Starship to make things like SLS obsolete, it has to be available first. Until then, it is just pure speculation. Is SLS more expensive than Starship development wise? Yes. But it is not the goal of a government to be profitable, nor is it to hand technologocal monopolies to eratic billionaires. Supporting alternatives is always good, and it maintains know-how and technology at different companies, which is also a good thing.