Price/TB is nearly identical for ancient SATA and new "high-end" PCIe 4 M.2 SSDs. The cost is EVERYTHING except the controller and the PCB. Which would be the memory, shockingly.
Do you think they have a yield problem? The price on chips usually drops when the production tech matures. I could believe the fab lines are running smoking hot, but surely by now lower density fab in all kinds of economies could be making this tech.
Maybe spending time making more GPU memory instead?