Oh please. IF you were correct and it was ALL about bang for the buck, then terrorists would simply be using conventional explosives.The destructive power of the Daisy Cutter is equal to about 12,600 pounds of TNT. 2,400 Daisy Cutters would get you one Hiroshima-sized blast (14.5KT).
Somehow, I think we would notice if you tried to smuggle 2,400 Daisy Cutters into NYC.
And that is why it isn't "all about the bang for the buck"...