Not to say that there is any adequate justification for such a high OOS tuition, but USC Greenville does have a few good reasons for charging so much.
1. As has been mentioned, they are a brand new medical school which has to deal with start up costs such as equipment and brand new faculty.
2. A large part of the problem has to do with school politics. For a long time SC has had only two medical school, MUSC and USC. Since there are only two schools, they have naturally been a little bit competitive. MUSC, being a more research oriented institution, believes that they are the premier school of the state. The announcement that USC was planning on starting a medical school in the upstate upset a lot of people in the lowcountry who saw this as an expansion of USC and not the creation of an autonomous school. Furthermore, MUSC saw this new school as a challenge to their ascendant position.
Thus, in response to USC's announcement, a lot of opposition came from the lowcountry, making it very difficult for USC to get this new school approved. The primary concern that was raised was that the state could not afford to support another state school. This concern was finally overcome by USC by agreeing to not take any state funds. This policy has made it very difficult for USC Greenville to start up - many believed that they would in fact not be able to start the school at all without this financial support. This situation has resulted in a school which is brand new and very financially vulnerable, a position which makes a high tuition an unfortunate necessity.