Back in 2007, I posted about the 12x18 granite surface plates for $25 with free UPS "shipping" (85 lbs of stone packed loose in foam peanuts or air pillows) from Enco:
Maybe Enco figured out that it averages three tries get one delivered intact when you pack them in air pillows.
By the way, I diamond-sawed the intact parts of the chipped ones I received back then, yielding a half dozen 2x18 granite straightedges, if anyone wants one for the cost of shipping 15 lbs priority mail.