$5B (2023: $4.7B) is actually the current yearly run rate for SLS+Orion+EGS. Thus, $5B is what the marginal launch cost would be if SLS was launching yearly, excluding $54B to-date costs of the three. Even NASA's official projections (which are always optimistic) don't show yearly launches, but if unreasonably optimistic numbers still make the point, why quibble over the details?