These are the visible costs of turnover:
* moving the new employee
* house-hunting trip for same
* airfare, hotel and expenses for all intervieweees, whether successful or not
* the cost of time for staffers to interview.
* The cost of overtime while the position stays  open
* amount of time spent in orientation by that new hire
 

Hidden costs
* Does the departure of one employee lead to the departure of others who are
overworked or who miss the person?
* What is the cost to your readership if you lose an experienced, locally
familiar person for one who writes or edits with less familiarity?
* Are there additional, competitive costs if this person goes to someone in
your market and takes readers/customers?

A rate of 2x the person's annual salary was cited, but I think that is lower
than the actual rate for technical or managerial positions.