According to http://www.storagenewsletter.com/new...y-data-problem
Out of 100 EB of disk storage systems expected to be shipped worldwide in 2013, 61 EB will be used to store copies of data, based on current rates.
This backup storage will cost $34 billion, or $560 per TB.
In addition, almost all of 90 EB of tape storage will be used to store backups at a cost of $1.9 billion, or $21 per TB.