There are several approaches to justify the cost of a telephone headset. At our firm we have a saying, Headsets are much less costly than visits to a chiropractor. Headsets add to the ergonomic well being and comfort of your telephone dependent and telephone intensive staff members, often reducing stress and job turnover. Headsets can insure against workman's compensation claims for neck and back strain caused by cradling a telephone handset between the head and shoulder.
Headsets are also the Number One telephone efficiency tool.
A simple cost analysis of a headset would be to take the cost of a headset, and divide it by the hours used per day over the life of the headset. Divide that result by the 5 days per week. Less than coffee and cigarettes. For as few as 12 calls per hour your costs drop to less then a cent per call. Some people use an oversimplified approach.