This study examines the incramental cost-effectiveness and benefit of a collaborative care program for patients with depression and diabetes as compared with standard care for such patients.  The study found that collaborative care patients expreienced fewer days of depression than the control and that total outcome costs were $25 higher over the same period.  The incramental cost per depression-free day was 25 cents (−$14 to $15) and the incremental cost per quality-adjusted life year ranged from $198 (144–316) to $397 (287–641). An incremental net benefit of $1,129 (692–1,572) was also found. 

Katon, W., J. Unutzer, et al. (2006). Cost-effectiveness and net benefit of enhanced treatment of depression for older adults with diabetes and depression. Diabetes Care, 29(2): 265-270. http://care.diabetesjournals.org/content/29/2/265.abstract