I doubt SpaceX’s internal costs are ~100m/falcon 9 launch, but companies need a markup to be profitable. 100m - 2B is a huge range covering everything from giving up on reusability and paying back R&D over a small number of flights to significant success resulting in a 90% reduction in costs per kg to LEO.

Also, having spent 5B on R&D and doing 5 test flights up to this point works out to 1 billion per flight. That’s not the actual marginal cost per flight, but when people say how expensive each shuttle flight was that’s the number they use. Nothing guarantees they continue to do Starship launches, they could fail it’s among the potential outcomes.