The IBM 3850 Mass Storage System (MSS), announced in 1974, held, in its largest configuration, some 472GB of data and cost $51,200 a month to rent or $2.3 million to buy. Data was held on tape which was wound onto cartridges which were stowed in the hexagonal rack (left). As data was needed the mechanical arm would pick the appropriate cartridge and read the tape. I never (knowingly) used one, but seek times must have been measured in 10s of seconds rather than milliseconds.    

That's a little less capacity than this Seagate drive (right), which costs $44.99 free and clear. Interestingly however, that's a price performance gain of just 33% a year. Of course, for an R&D team looking into the future, that's a fairly aggressive stretch goal for one year, let alone thirty seven.

One cartridge in the 3850 (left) holds 50 MB of data - on tape!