Ask HN: Did the NSA impact the cost of hard drives?

Due to Edward Snowden's leaks we know that the NSA has been collecting astronomical amounts of data. Presumably this is stored on hard drives somewhere. I imagine that the storage requirements must be enormous so my question is how could the NSA's purchasing of so much of the global HDD stock go unnoticed or unquestioned? Or am I overestimating their storage requirements?