The specific Rolls Royce engines used on the A380 were developed specially and were a leap in efficiency at the time the aircraft was introduced. The Dreamliner

The specific Rolls Royce engines used on the A380 were developed specially and were a leap in efficiency at the time the aircraft was introduced. The Dreamliner and A350 use engines that are of the same technological level, but the airframes are cheaper to operate because they are made from composites and so are 20-30% lighter per passenger.