Maggie
It is impossible to tell you what is acceptable or not. It is all relevant to what you are doing to package your items, whether you have great discounts from your delivery service and the type and cost of what you are selling and shipping.
We dont charge exactly what our cost is as we never know exactly what our cost will be to ship. i try to inflate each charge somewhat to cover my time and costs in packaging.
As an example, I spend about 15 minutes, custom making boxes for violins but I dont have any cost for the box materials used.
In other cases, I spendmoney on bubble wrap but no time on making a box.
Also when shipping my items, people expect a higher than normal shipping charge due to the nature of what is being shipped and their desire for it to arrive safely.
There are alot of variables to consider. These would include looking at what and how much your competition charges for shipping similar items.
Malcolm