2. Seawolf Class

At more than $4 billion apiece, Seawolf Class submarines were the most expensive in history. But they were designed for a mission that brooked no failure; stalk and destroy Soviet ballistic missile subs before they could launch their weapons. Designed to be extremely fast and extremely quiet, the high price tag and diminished Soviet submarine threat with the end of the cold war caused the program to be cancelled after the first three boats were delivered. One of them, the USS Jimmy Carter, has since been converted into a spy sub.