We work on a cost+ structure - which basically means for the brands that we work with, we share open cost structure + our margin. Our margins are on reducing scale based on the aggregate dollar value of the purchase order.
So when you order in bulk you make savings in at least 4 out of 5 factors affecting your product costing.
Are looking for questions on how to calculate product costing?
Do you need more information about how are our margins calculated?