I don't see the real problem.
The military has to rent space close to the President, because of the "nuclear button" that has to be close to him in case it's needed. So that means they can't rent a space in another office building nearby, due to the time it would take them to even cross the street in NYC traffic.
As to the cost? Compare that to how much the DoD pays for ONE weapon system. We've paid over $400 BILLION to Lockhead-Martin to come up with a new fighter jet, and it's still in development. Then, we'll still have to pay over $1 BILLION per plane ordered. See where I'm going with this? For the cost of one plane or tank or ship, the DoD could rent space in that building for hundreds of years.