I'm very wonder what is the HDD BOM cost.Mainly, disk, heads, controller, and others.
And also SSD BOM cost.NAND (128GB), controller, PCB and others.
Not sure what info your looking? Also alot depends on where you live and what is available in your region differs from one area to another. And you might noticed this is a international forum so asking question you want to relate to where your from to get better info.
You've also got to consider there is more cost than just materials. For instance, the raw material of computer chips is sand. It costs literally pennies a ton. However it passes through many expensive processes on its way to becoming NAND chips. There's also 'shipping and handling' to consider.