How thick is this ploprof crystal, I wonder. Thickness, even more so than diameter, does seem to play a big role in the cost. So my guess would be they'd rather pay a factory laborer $0.10 an hour to CNC a jig that allows them to register a thin sheet of sapphire on top of inexpensive glass with the proper alignment to fit the watch. Once they have the jigs, they can knock these things out with cheap materials that delaminate in water. And it's a solution that does seem to achieve the right look if you never get it wet.
And it reminds me of the original UPO crystals. I still think there is something funky with those crystals, which are among the thickest out there. They were originally 3.3mm (now most I see seem to be under 3mm though) and while not a two piece lamination, definitely questionable. Whatever they are, the failure rate for recoating AR is extremely high with those, and I've never seen this happen on any other sapphire crystal.
Another thick one is the 187 crystal. But this seems to be legit sapphire, and probably the highest quality rep crystal out there. Heavy, coats beautifully, and is crystal clear.
Dunno...