Forum member emazers informs us that the online LEGO Star Wars exclusive 10188 Death Star and 10221 Super Star Destroyer is currently on sale at Amazon for $359.99 each (reg.$399.99). Note that the Death Star has been out for more than 4 years already so it could be coming to its end very soon.
As always, free shipping and no tax for most states. More of their hottest LEGO deals can be found here.