Source: Center for Supply Chain Research, Penn State University. As the INV cost goes up the COLS seems to go down. organizations are usually willing to increase the inventory cost only until total costs start to increase or stated in economic terms, to the point a which the marginal savings from reducing lost sales cost equals the marginal cost of carrying additional inventory. Total cost is a sum of INV and COLS. increasing inventory costs (either by increasing the inven- tory level or by increasing the reorder point), organizations can usually reduce the co of lost sales