Again, no one knows. Not $700 billion--that's the amount we're paying for distressed assets, some of which will yield profits. The entire portfolio of fire sale securities may lose money, but it's unlikely to be anything close to the entire amount.
In some sense, the reason to do the bailout is that we don't know. I don't want to give money to GM because I have a pretty good notion of the scale of a GM collapse. Some people will lose their jobs and get new ones, the steel industry will take a hit, and a lot of managers will be looking for another line of work than pushing ugly, underperforming cars. On the other hand, I have no idea how far a bank collapse might spread. And I'm really not eager to find out.