"Each drive contains 128 32-layer 128Gbit Samsung 3D V-NAND chips"
Surely not? It can't be possible to fit 128 chips inside a 2.5" drive. They must mean 4 chips each containing 32-layers (effectively 128 layers, each storing 16Gbytes/128Gbits).
Either way, 128 layers of silicon must consume a large area of wafer. No wonder they're so expensive. I can't see there being much room for price reduction / economy of scale in future.