What they say:
Policy overview
When a buyer wins an item or uses Buy it now to purchase an item, they're obliged to complete the purchase by sending full payment to the seller.
If a buyer doesn't pay within 4 days, sellers can open an unpaid item case in the Resolution Centre. If the buyer still doesn't pay or reach some other agreement with the seller, eBay may record the unpaid item on the buyer's account.
When an unpaid item case closes without payment from the buyer, sellers are eligible to receive a final value fee credit to their eBay seller account. Also, if they relist the item and it sells the second time, eBay may refund the insertion fee for the relisting. Learn more about how the free relist policy works.