We have a sationery store that has products with good prices, but we do not sell much because people leave checkout because of the shipping fees. This is a fact analysing google analytics.
However, we can give discounts in every product if the client buy the pack. For example, if a client wants to buy a pen is one price, but if he buys a pack with 12, we can give a discount. Although, every product has a different number of items in a pack what makes what i want more difficult. For each product, we have a record of how many a pack contains.
I would like to give this discount value not in the product, which varies depending on the item, but in the shipping. Actually, we are giving discount on the product, but i want that the client think he is paying less for the shipping. This value to be subtracted from the shipping would have to be the same of the discount. Why i want to do this? Because as I said, we really have good prices and i would like to give the client the idea that he is paying less for the shipping.