As I understand it the cost is not just the room its to sort out No9.
To be honest I dont think the cost is that big considering it is a grade 1 building - you cant just run the wires where you like it all has to be done in an approved manner (And rightly so)
Add to that the cost of cameras etc (an no doubt security equipment you wont for obvious reasons be told about) seem about the right sort of ball park.
We need to remember this is how the World will see us. It's like financial companies that have an office in the City, yes you could do your job elsewhere but if you want to attract the big bucks you need to look like you are doing well. And we need to attract the big bucks - UK open for business it needs to shout.
I was in two minds about the blue though , seems a bit bright but it does set the red in the flags off a treat.
I think it does need a picture of 10 downing street on the wall between the flags though.