JohnnyZemo
Adventurer
Last year they got an autographed adventure for $30 more than the cost of the slots. This year you are paying $100 dollars more than the slots. I would hope it is more than just a signed PHB. The WOTC staff is fairly happy to sign books if you run into them at the con and the book is only $50. I doubt they'd charge that much extra simply because it's a PHB and not an adventure. You'll get SOMETHING else. Maybe not a book.
Maybe you get a PHB and a few con-exclusive miniatures (probably alternate paint jobs of minis in the first set of new D&D minis)?