If he hasn't paid and you still have the item then dispute centre isn't likely to accomplish anything useful. They can't make him pay. Better off sending him a message saying " You send me 15 bucks to cover my ebay fee's and time shifting this thing around the garage (I assume it's not that small if it was pickup ony) and I'll relist and leave you good feedback" Then send a second chance offer to whoever was the next highest bidder on the Auction.

If the guy can't handle 15 bucks for his mistake then he's a tool and hit him with it then.