if the airframe is written off, sure there must be substantial damage, but keep in mind that this was a 26 year old ex Northwest airframe, and Delta will be phasing out the 747 fleet by 2017. Not trying to be a smartass, and not advocating flying into hail or cb but the resale value of that 747 probably wasn't extremely high even before it was damaged. iI a decision to write it off is taken, it reflects repair cost > residual value, not "damage" alone.