Three years ago, anyone who would dare to question the cost of anything would have been accused of hating our heros, betraying our country, and not understanding the importance of 9/11. Now, perhaps if someone had challenged the costs and introduced reality sooner, we wouldn't be in this position and he/she would, in retrospect, actually be a hero.
By the way, that billion is not the end of it. The real cost of this memorial is $1 B plus the additional cost of every other project from the Freedom Tower to the Bus parking caused because nothing that was actually useful could be located in America's largest retainer wall (literary license, it may not be the largest).
But don't worry about the outcome. All of the wealthy preservationists will rise to the occasion and toss in every cent needed to protect the historic cement slabs. And the money tourists spend on pizza around the site will drive the economy of New York to new heights.