[Someone]

I don’t think it’s fair to expect hard drive capacity/$ to grow exponentially forever.

Certainly for consumer hard drives, there’s a cost of getting the drive to the customer (transport, shop rent, employee salaries, etc) which is, at best, fixed.

If manufacturing costs drop to zero, price will approach that fixed cost (plus any markup sellers manage to extract, for example by marketing their drives as better/more hip/etc.)