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If you were running a restaurant: rent, staff, advertising would be fixed costs, they are predictable and should remain fairly constant from month to month. Food supplies, disposables such as napkins, are variable costs, they would change based on the level of business i.e. how many customers, or meals you have to prepare.
In manufacturing your cost of goods sold should drop as you manufacture more product. This is economy of scale. The larger the order of raw materials the less they should cost you per unit.