I assume we are talking aluminum wheels. So very high quality wheels will be forged (or some of the new methods of spin casting that increase strength) while less expensive wheels will be cast. I was told (so I'm not certain this bit is true) that wheels with a JW mark indicate that they have passed some Japanese testing, and are possibly better than wheels that haven't been so certified. But forged wheels tend to be big bucks ($500+ each, at least in the BMW world). At the lower price points, I think you are often paying for the name, styling, warranty, company reputation, etc.--some of this may matter, some of this may not.