The importance of a nurse leader to understand variance reporting

What is it important for a nurse leader to understand variance reporting? How does this reporting become a valuable tool?
Because staffing is usually the most expensive resource in the provision of care, what reports would provide you with valuable information for this expense?
Contract labor is usually the most expensive man-hours. Why?
What is a cost-to-charge ratio? Why should a nurse manager understand this ratio, and how would he or she use it?
Finance departments regard nursing units as not being revenue generators. Why do you believe they are inaccurate in their assessment?
In the new value-based reimbursement environment, what other measures can a nurse manager take to enhance reimbursement and prevent revenue loss?