The assumption that the cost of content storage is merely the cost per Mb of a hard drive takes no account of the cost of accommodating the drive into a rack, maintaining the environment around it, providing backup, migrating content to future drives, employing skilled support and security staff, and so on. Estimates vary between two and three times the basic drive cost. We will refer to this overall cost as the “unstructured content footprint”. A complete analysis of this footprint would include the much more intangible “cost” of potential data breaches, data protection infringement, legal discovery costs, and general productivity reduction from poor searchability. Our respondents in Figure 3 feel under considerable pressure to reduce these “dark data” risks.

The above quote is from the AIIM white paper “IG Policy versus IG Reality – bringing your wild content under control”