OK, I know we just mentioned 10TB HDDs, but how about this one, Fixstars is releasing a 13TB SSD. Now before you run to the stores, this is enterprise class stuff and the firm will not even share the... All hail the 13TB SSD
Prolly depends on the SSD and mechanical HDD... But SSD's are still quite new, need to cover R&D costs, firmware updates, think about logistic costs, marketing, sale volumes, assebly time, warranty, support, how much people are willing to pay... Having worked at one companys R&D writing code, you cant just say something should cost less than something else based on component costs alone.
This thing is expensive and slow. Would be better to build SSD raid or even better to get raid made from PCIe/M.2. But I guess it has its use somewhere.