How much is a barrel of oil worth - one pelican, 50 lbs of shrimp - a months rent? Money isn't the object - corporate responsibility is. From what I read BP knew the blowout preventer was defective - had to reduce the pressure when testing, it was just a matter of time...
My feeling is - All these undersea shenanigans are more for show than anything else - prove to everyone that they are trying. PR. They really know that each one has a minimal chance at succeeding.
What they probably know, but won't admit, is that the only true probability of success is the two relief wells. All they got do is intersect a 5 ft diameter hole 8 thousand feet down rilling at a 45degree angle. What do you think, could you imagine it working.
More likely they feel if they get close enough and relieve the pressure by pumping out all the oil that the other leak will slow dow to "manageble" levels.