What if you consider offline products. I noticed a lot of people like quantity and quality while some don't still want to give what it takes to acquire both. I feel these two things are required to get customers attention. But you have to be smart so you don't end up cheating yourself.
You can decide to offer them discount when they make large purchase.
You can also offer them free delivery and provided it's within your axis.
Good customer service is great strategy, so many don't consider it, but it works well.