Most people think that the proposed bailout will cost $700 billion. In fact, it is not limited to $700 big ones, and will probably go much higher.
Specifically, Paulson's draft bailout plans says:
"The Secretary’s authority to purchase mortgage-related assets under this Act shall be limited to $700,000,000,000 outstanding at any one time."
That means that Paulson could buy a couple hundred billion worth of assets one day, and then - a little later - buy another couple hundred billion, and so on.