Good discussions and suggestions. For anyone who would like to borrow from experts in this area, I would suggest contacting work force administrators and or accounting folks in the established Telecom industry (the former Bell companies) they are truly expert at this. I speak from experience.
They would typically use a “fully loaded labor rate” for a job title, that would include the appropriate level of allocated fixed and variable expenses along with the average wage for the job title. Then they would probably divide by the total calls handled. (Not offered). I’m working on this issue in a very small company now and it’s hard to get my arms around the allocated expense. I’m starting with wages+ benefits.