What is the average cost of a gigabyte?

As of 2010-01-19, an internal terabyte hard drive costs about $100, so a gigabyte costs about 10 cents USD.

2010-10-30 (October 30):

For the Western Digital 2 TB My Book Essential Desktop External Hard Drive, per gigabyte:

• 7.5 Canadian cents
• 5 cm3 (which is a 1.7 x 1.7 x 1.7 cm box)
• 1.4 grams

(Two TB comes in a 14.1 x 17.5 x 20.2 cm box)