A costing system. The costing system includes a costing model and a costing engine. The costing model records parent-child relationships between a plurality of stages of a production line, and at least one valuation type for each stage. The costing engine retrieves a group of valuation type combinations corresponding to the parent stages of the target stage from the costing model, and combines the target valuation type corresponding to the target stage with valuation type combinations corresponding to the parent stages, thereby generating a cost identification, and costing results accordingly.