The First Line of Support
http://www.sdtimes.com/content/article.aspx?ArticleID=29249

Butow, Eric
Software Development Times
2006

Abstract:

Customer support costs account for as much as 60 percent of a high-tech company’s total costs. Documentation is the first line of support for most customers, and customers usually use documentation to find the answer to a problem they’re having. The inevitable result of poor or nonexistent documentation is that more people try calling the customer support lines for help.