Re: No worries
Spacenews says "The problem with the Space Launch System is that it is a fully expendable rocket that could cost between $1.5 billion to $2.5 billion to launch. NASA is struggling to make the SLS more affordable to operate"
Where did you get the half billion cost per launch from?
Meanwhile, SpaceX is quoting costs of $62 million for the Falcon 9 Full Thrust and $90 million for the Falcon Heavy, both of which have actually flown. The ESA has a target price of 90 million euros for the upcoming Ariane 6. Meanwhile, the SLS remains expensive vapourware and by the time they actually finish it, SpaceX may well be ready with their BFR.
Personally, I would be quite surprised if the SLS project ever actually gets used at the cost/performance it has.