Contrary to the crowd I have bought used cassettes. But I wouldn't buy that one. A cassette has to look pristine and the story has to be something like "I only rode it a hundred miles and then swapped it for better gearing". The price also needs to reflect the risk and to me $60 doesn't in this case. I do agree that there is no way to know how worn a cassette is or how much life is left simply by looking at it.