Consumers were conditioned to expect falling prices as time goes by.. after the price gouging that went on after a slight 5% loss in production due to the flooding in Thailand and Malaysia (2011-2014) all that changed. HDD mfg's kept their higher price trend and wholesalers got in on the collusion action making street prices all that much higher.
All of this combined with overall economy inflation (your $1 doesn't go as far) means things just COST more than they used to, so price per GB looks to flatten out anyway. That leads to $350 - $500 10TB hard drives.. Over time this will shift, but it's not a curve.. it's an almost indistinguishable from a parallel line decline. Just look at cpu, ddr memory makers and gpu makers.. they're off to the races with sky high increases.