Every platform has its ups and downs as well as particular fee structures.

So the solution is to add some extra amount into your selling price here at eBay.  For example, I add about $2.50 onto my prices here compared to the prices on my website and that helps to cover the fees eBay calculates from both the sale amount and also the shipping amount.

If your profit margin isn't satisfactory then increase your price and/or find other things to sell which allow you to mark up enough.  If people really want it, they will pay you for it.  If they can find it somewhere else for a different price, change to selling other things which will keep them buying from you.