Spare capacity, mostly. That’s why they have higher endurance. If you want to double the endurance of a given drive, tell the controller to allocate twice as many spare blocks and report less capacity than you would otherwise.

In this case, you are also paying a premium for the PCIe attachment instead of SAS, and a lot for price elasticity. You see, with drives like these you slash space and energy consumption in relation to HDDs by a large number, and that allows you to pay a premium for the device, because, at the end of its lifetime, it’ll have more than covered the cost difference in saved space and energy.

The word "enterprise".

surely you don't actually think that's realistic pricing?