Cory at BoingBoing blogged David Isenberg’s tracking of the historical cost of rotating magnetic disk storage.

YEAR — Price of a Gigabyte
1981 — $300,000
1987 — $50,000
1990 — $10,000
1994 — $1000
1997 — $100
2000 — $10
2004 — $1
2010 — $0.10

I can remember buying an IBM 5022 disk subsystem in the mid 1970s composed of two 2.5MB platters (one fixed, one 5440 removable cartridge). According to the 1971 IBM press release (http://www-03.ibm.com/ibm/history/exhibits/system7/system7_press.html) the purchase price was $16,225, which comes to $3,245,000 per gigabyte in 1971 dollars or $16,999,437.09/GB in 2009.