It's not uncommon for the land under such buildings to have 100+ year leases. That much money and time put into that much building requires very long terms. Maybe Apple bought the land outright, but I'm certain they're thinking longer-term than 10 years here... as was Sears at the time they built their tower.
This also doesn't account for the annual maintenance costs of such a grand building. Apple's sitting on top of a big pile of money today, but that may not be the case 20 years from now (as was the case for Sears)... the maintenance costs will only increase as the building ages.