I don’t believe they are going to be able to enter the earth’s atmosphere with a Starship designed to land on the moon. Crews and return samples will need to be transferred to another craft capable of reentry?
I wouldn’t doubt those 4 main SLS single use engines costing $500 million for the first stage alone, that’s not including the rest of the first stage costs. SLS sounds like a pretty expensive way to get to orbit. IIRC, the launch site itself cost over 3 billion.
I think Musk is talking about an unmanned demo. Some are speculating that it won’t have thermal protection and that it will return to Earth orbit. I’m guessing it will perform as a test article for the lunar lander that NASA just contracted for. The lander will make several back and forth trips between lunar orbit and the Moon’s surface.