Those are also:
- More expensive than Starship, or
- Took longer to develop than Starship, or
- Are significantly less ambitious than Starship
(and those are definitely not exclusive ORs)
- More expensive than Starship, or
- Took longer to develop than Starship, or
- Are significantly less ambitious than Starship
(and those are definitely not exclusive ORs)
SLS use leftover engines from the Shuttle era. Yet it still cost 160 millions. Each. Thrown away after each flight.
Vulcan is a conservative design with no reuse. It also uses BE-4 engine, which costs them nothing to develop.
- Not sure where you're getting the SLS number, the GAO report at https://www.gao.gov/assets/gao-23-105609.pdf claims, "Since 2011, NASA has spent $11.8 billion to develop the initial SLS capability."
- I think the marginal cost is a fair question. The whole party line out of NASA was that this time Moon exploration would be sustainable. If each trip costs > $1B before you even put a payload on the rocket that's a big problem.