NASA does not deny the over $2 billion cost of a single SLS launch

"NASA is working to bring down the cost of a single SLS launch."

For the first time, a government cost estimate of building and flying a single Space Launch System rocket in a given year has been released. This estimate of "over $2 billion" came in the form of a letter from the White House to the Senate Appropriations Committee first reported by Ars this week.
Dont forget development costs
What the White House cost estimate did not include, however, was development costs. Since 2011, Congress has appropriated approximately $2 billion per year for the "development" of the SLS rocket (this does not include hundreds of millions of dollars spent annually on ground systems "development" for the rocket at Kennedy Space Center).
Adding all of this up, the true cost of a Space Launch System mission with Orion on top in the 2020s, including the rocket's development but excluding ground systems and Orion development costs, appears to be in the ballpark of $5 billion per flight.

Let's hope the astronauts are served more than just pretzels after takeoff.