That's a surprise. I've been doing business on ebay as both a buyer and seller, since about 1996, and have never been screwed on a deal.
Sure, I've received an item here or there that didn't meet expectations, but every time I've contacted the seller and we've worked something out, usually a return but sometimes a partial refund to make things right.
Likewise in reverse. I once sold an item as "good" that I hadn't realized was "bad". I just refunded the buyer the purchase price and let them keep the item (two pieces, one was good). Everyone was happy.