The ecommerce software I have seen you have to pick one of the following methods for the whole store:
- price per item
- price per dollar value of the order
- price based on weight
There is a risk of loosing money on some items in your store no matter which if the above methods you choose.
How have you decided to price your shipping costs to the customer?
Have you found an ecommerce software package where you can have more than 1 type method of costing shipping costs in the same ecommerce site?