This is a Quora question I was asked. My answer is below.
In food/consummables, manufacturers publish their price list, which in my experience does not normally include discounts for volume-based orders.
If volumes are very low, then there may be a higher cost to cover the additional administrative and logistics costs associated with smaller orders, but that is usually done on a case-by-case basis and not normal. If the order is small and requires unique shipping or logistics, which can mean more administrative hand holding, then this makes sense to charge a higher list price.
However, in general, it is easier for the manufacturer to just post its price list and not worry about charging higher distributor pricing amounts for small orders or small vendors because it is more of a hassle to manage that.
When volumes become significant, then the manufacturer can offer discounts on a case-by-case basis.