In 1956, IBM introduced the 305 RAMAC computer, which was the first computer to include a disk drive. Prior to this, computers stored data with core memory, tape, or drums. The magnetic disk provided more storage in less space.
The 350 Disk File consisted of a stack of fifty 24" discs. The capacity of the entire disk file was about 4.4 MB, which was an enormous capacity for 1956. IBM leased the 350 Disk File for $35,000 per year. In early 2007, you should be able to get a TeraByte hard drive (with nearly 250,000 times the capacity of the original IBM drive) for just $399. (info from CEDmagic)