A380 is same as 747. It was only the 777 that went for 8000ft. Thats why I think Boeing are being a little economical with the truth. On the average 747 flight the cabin altitude will be between 4-6000'. In fact ive never seen 6000' because youd have to go over 40000 to see it.

On flights to mexico city the cabin often DE-pressurises to land.