The floppy disk
eBay price: $1 - $20 (for a pack)
The floppy disk drive, or FDD, was invented by an IBM inventor in 1967. Used in early computers, they held about 360 kilobytes -- which couldn't hold even one Katy Perry song.
Floppies were phased out in the mid-1990s with the rise of CDs. It would be hard to buy floppy disks these days, let alone use them for storing data. They could make for good drink coasters, though.