The most expensive wartime weapon was a system, not one device

What was the most expensive single weapon of the Second World War?

The atomic-bomb delivery system is a strong candidate once the B-29, Manhattan Project, bombsight, bases, campaigns, and logistics are counted together.

The atomic bomb cannot be costed as an isolated procurement item in this comparison. The B-29 program, Manhattan Project, and Norden bombsight formed part of the delivery system, as did the campaigns, airfields, shipping, and support needed to place the weapon within range of Japan. The total cost therefore depends on the operational system that made the strike possible.