Not just heritage, the SLS is basically what you get if you move the Space Shuttle engines onto the propellant tank and remove the orbiter vehicle. Then discard

Not just heritage, the SLS is basically what you get if you move the Space Shuttle engines onto the propellant tank and remove the orbiter vehicle. Then discard the reusability requirement and you've got SLS. In the process of this, everything is being modernized. This is where all the cost comes from.