Well buyer can just ask for their money back via Paypal and they'll prolly neg you and blame you for it.
You then obviously lose out as you paid the postage charge and you dont really have any grounds to seek your refund on your auction fees with eBay.
Yes eBay is for the buyer only, they dont give 2 hoots for sellers no more. Would recommend you type the following "contact user request" in the help bar and follow thru to get your buyers details and their telephone number and phone them.
People tend not to be keyboard warriors once they get a phone call. I'm a powerseller BTW.