"… SLS cost is almost two-thirds of NASA’s entire annual budget …"

Robbing NASA blind: 

Notice that [in this scenario] the Falcon XX launch cost for this operation is comparable to the current cost of paying the Russians to ferry our crews to the space station each year, while the low SLS cost is almost two-thirds of NASA’s entire annual budget, and the high estimate exceeds its budget by over $4 billion. We cannot know the actual cost of an SLS operation since no launch cost has been posted. The only comparable costs would be if we were using a fleet of expendable cargo aircraft, which were thrown away after each cargo flight to a distant shore due to lack of aviation fuel at the destination.