I sell used camera lenses and for the majortiy of the sales, there's no problem what's soever.

BUT, now and again I get a complaint from some buyers that the focus ring is too tight or too loose, zoom ring is too tight or too loose or the corners of the picture is too soft (not sharp), etc.

To keep the customers happy, I give them some discount or accept the return of lens and rerund in full including both shipping costs both to and from.  If the customer accepts the discount, it's not too bad, but if they decide to return the lens, the cost of return freight is sometmes prohibitively expensive, especailly from EU countries.

Now, for an old, used lens, surely there has to be some tolerance level for subjective issues such as mentiioned above.  I understand if the focus or zoom ring doesn't move at all or very sloppy then it's definitely faulty and responsibility is mine.

If I refuse to give customers the reimbursement for return freight for such cases, am I within my rights?  If the cusomer decides to file a complaint against me, which side will eBay take?