Business & farm

I keep reading that shipping supplies (boxes, bubble wrap, etc) and shipping postage costs (USPS, UPS, etc) do not count toward COGS because these were not used in direct manufacturing of the item being sold. I guess the shipping costs don't matter too much because I don't spend it unless someone buys something, but as far as shipping supplies go, it seems like those would go under general business expenses.

Can you clarify?