Volume discounts are so natural and effective. People just get them.
As customers, we expect a pack of 32 water bottles to cost less per bottle than a 12- or 6-pack. If the discount is significant enough, we may even upgrade our purchase to a higher volume than we originally intended. As marketers, we take a small hit on margins to increase the average order size and overall revenue.
There are many ways to discount products and bulk volume discounts, in particular, can be applied to nearly every business. You can offer a fixed rate if customers have free reign over the quantity they purchase. Or, if you have a few sizes, you can carefully calculate discounts for each offer.
Another practical approach is to find the average quantity purchased and offer a discount for buying a little more. If the average order includes 2.3 products, you can offer a 10% discount on purchases of three or more items.
There are many ways to implement volume discounts, and most businesses can utilize some variation to improve their average transaction size.