Does it make sense for a volunteer organization to charge its volunteers money?

This particular one sends volunteers to developing countries to teach and help out in other ways. It is called ProjectsAbroad. The website and booklet/brochure seem to be proof that the organization is legitimate, and they explain the fee as a result of no government funding and travel/food/housing expenses. However, charging volunteers a fee still seems a bit odd to me. Has anyone had experience with this organization or know of a similar one that does NOT charge its volunteers?