If you look closely in that article, you'll see the price that review board assumed for the SLS was $500 million. That's a number that SLS people like to throw

If you look closely in that article, you'll see the price that review board assumed for the SLS was $500 million. That's a number that SLS people like to throw around, but it is far, far less than many outsiders expect it will cost. The SLS is only expected to fly once every couple of years in the mid-2020's, so one or two years of the full cost of the program needs to be booked against each launch. Each will have an effective cost of $2 to 4 billion, and that doesn't even include any fraction of the enormous development cost. It could easily be worthwhile to spend $500 million to cut a few years off of a $2 billion mission. It's much less likely to pay off when the cost is $2 to 4 billion. That's the equivalent of three to eight extra entire Discovery-class missions, or two to four New Frontier missions.