Cost containment is a priority in most social care systems and there is an increasing importance in using staff in the most effective way within available resources. Previous work has revealed that the social worker does not remain in the profession for as long as health professionals and this situation has far-reaching consequences for workforce planners. Given that a major overhaul in social work is underway, it is important to address questions such as how much could be saved if social workers were to remain in the profession for longer and how we should target the limited stock of professional expertise (or human capital). In this article, we have explored the full opportunity costs of qualifying social workers that incorporates the human capital cost implications of developing a skilled workforce. A survey of Practice Educators has been carried out in order to determine the actual cost of the practice learning placements undertaken. When all the costs are added to the cost of providing a social worker, the unit costs increase is more than twice or three times that of health professionals. This is due to the short working life and highlights how important it is to establish the causes of social work attrition.