yes, i have seen that warning too. i just ignore it. ebay is comparing your shipping to others in the same category, but it doesn't mean the items are all the same. there are a lot of variables that can make similar items in the same category weight much more, or are a bigger item. then you have the free shipping people throwing off the curve.
it's getting ridiculous. basically ebay wants everyone to give free shipping so they can benefit from taking a larger feee from your starting price.
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