Value: putting U-boats down, which doesn't necessarily mean sinking them. Nothing else even gets close in terms of historical importance, vital part in turning the tide against the U-boats, enabling build up to D-Day, cost then becomes almost immaterial when measured against value. As per previous poster: B24 (with Bulloch)? Leigh Light Wellington (U-boat SURPRISE!)? Cat?
I'm sure the little training aircraft and the helicopters are very useful
