Neither has SLS entered orbit to be fair, and it had a massive development budget and a half decade head start (plus existing engines).
Everyone is taking Starship reuse as an assumption because of SpaceX’s earlier work. It will likely be less easy than people think with such a massive vehicle, but even fully expended mode Starship will loft far more mass at less than an eighth of the cost of a SLS launch.
Everyone is taking Starship reuse as an assumption because of SpaceX’s earlier work. It will likely be less easy than people think with such a massive vehicle, but even fully expended mode Starship will loft far more mass at less than an eighth of the cost of a SLS launch.