1. A computer-implemented method of sequencing cost calculations, said method comprising: creating at a computer system a processing sequence for a plurality of cost groups, each cost group comprising one or more inventory premises and one or more items and said cost group being associated with its own corresponding bill of materials classifying said one or more items, the cost of at least one item of a first cost group of the plurality of cost groups depending on the absorption cost of another item of a second cost group of the plurality of cost groups, the absorption cost based at least in part on the one or more inventory premises for the item of the second cost group, and said processing sequence comprising a plurality of hierarchy levels; calculating, via the computer system and using said processing sequence in an iterative process, the cost of an item of said plurality of cost groups; and repeating, via the computer system, said iterative process until the costs of a plurality of items of said plurality of cost groups have been calculated.