Relying on the proceeds of each sale to cover the delivery costs of that sale is no way to run a business.  Your buyer has paid and you have confirmation that the money has been received, you should ship without delay to the buyer.  If you were running a bricks and mortar business you wouldn't start the day with nothing in the till, you'd have a float to use to make change from the start of trading.  And you wouldn't make credit card customers wait until their funds have cleared to your bank account before letting them leave the shop.  eBay is not ruining your business, they are taking reasonable measures to ensure your customer can receive a refund if it proves necessary.