Regarding today's announcement of "Willis Tower" being sold to Aon for a whopping $30 Billion dollars; can I trouble someone to help me wrap my head around this? We've seen recent, relatively large, office tower sales between $750 million - $900 million, and I recall Trump Tower being valued at over $1 billion, which is somewhat similar in scale to Sears, but how on earth is Sears valued at $30 billion?