Methods and systems are directed to allocating costs of storage arrays to logical disks. A fully loaded cost of storage of a storage area network (“SAN”) is calculated based on capital and operational expenditures of the SAN. Data is stored in the SAN in logical groups partitioned into logical disks. The unit rates of the logical groups are calculated from the capacities and utilization of the storage arrays that form the SAN. The unit rate of a logical disk is the unit rate the logical group to which the logical disk belongs. The storage cost of each logical disk is calculated from the unit rate of the logical disk and the utilized capacity of the logical disk. Methods also calculate cost of unallocated capacities of the logical disks, storage arrays, and the SAN, in order to evaluate efficient use of the SAN storage resources.