Note that this set is for a special, Amazon-exclusive Premium Edition. Check out the Attack on Titan PE for a general idea of what may be in it.
FUNimation WILL release a standard edition, likely 3 Blu-ray discs and 4 DVDs, that will be priced like normal, though the way the announcement slide was worded made it seem like they will be separate releases instead of a combo pack (I hope so).
Contents of either PE have not been revealed but you can probably expect at least one of them to include digibook packaging, multiple soundtracks, keychains, an art book, another book with interviews/crew comments, perhaps a pair of Ed's goggles, and I bet we'll see some kind of display piece (whether it be the Bebop or the Swordfish, a figure, an Ein plush, or a bust of some kind). Part of me hopes one of the PE will be a Steelbook.