EDITED FOR CLARIFICATION
In your situation, the shipping expenses would be considered a normal/general business expense and not cost of goods sold.
Containers and packages that are an integral part of the product are a part of your cost of goods sold.
If they are not an integral part of the final product, their costs are shipping or selling (normal business) expenses.
For more information, you can reference the Line 39 other costs instructions in Chapter 6 (How to Figure Cost of Goods Sold) of the IRS Publication 334, Tax Guides for Small Businesses, linked to below:
https://www.irs.gov/publications/p334/ch06.html
