Some airlines put 290 passengers in a 747-400, e.g. BA and ANA. Some will put 475 seats in a A380, some 650 (EK)
Determining the CASM (Cost per Available Seat Mile) is the marketing guys favorite toolkit (selecting low density configurations for the competitor : Boeings Randy's) & the big public believes it.
I think it would be more fair to compare an 11 abreast A380s to 10 abreast 747s looking at seat widths..
Lufthansa selected both the 747-8i and A380-800 and say the A380 is more fuel efficient (not that it says much..)
