eBay has a pretty detailed page explaining the 1099-K form -
https://www.ebay.com/help/selling/fe...-1099k?id=4794
Shipping Charges are part of the total sale price so they will always be included in the total gross amount of income. A seller can deduct the actual amount they paid to ship items though when filing their taxes.
As always, consult a CPA if you are unsure how to reconcile your 1099-K and report it on your taxes.