I don't think "no idea" is fair. We don't have exact numbers, but there are various statements out there that give clues. Even the highest estimates I can put together put Starship far cheaper than SLS.
You have to consider that Starship has not reached anywhere near the operational goals for Artemis, and there is no realistic time line for when it might. So we really do have no idea how much it might cost by the time it reaches the milestone SLS has already cleared (successful flight in lunar orbit, with a full payload that it successfully deploys).
You have to consider that Starship has not reached anywhere near the operational goals for Artemis, and there is no realistic time line for when it might. So we really do have no idea how much it might cost by the time it reaches the milestone SLS has already cleared (successful flight in lunar orbit, with a full payload that it successfully deploys).