Remember Sneakers? That's how the movie's device would have worked.

Consider this: the NSA stores all of the IP packets ever communicated via our domestic Internet infrastructure. So, if it is interested in a particular communication session, it can retrieve the packets constituting that communication session, send them – in proper sequence and on a one-by-one basis – to The Hammer, which will decrypt the contents of each packet, and then the whole communication session can be eavesdropped upon.

When NSA's Utah data center went online, mechanical hard drives were nearly impossible to get. While there were some natural disasters and stuff that could possibly affect availability and ultimately price, over the years prices haven't really recovered to where you would expect. Even while SSDs are cratering in price right now, mechanical drives are still $15+/TB. Moore's Law expects prices to drop exponentially over time and it used to happen. Want to guess which type of drive you buy when building large scale archival of data?

Now this could totally be caused by consolidation in the industry, making it way easier for a few producers to implement a formal or informal price fixing scheme. But it could also be caused by relatively high demand for their product, too. Somebody archiving all Internet traffic would certainly fit the bill.