It’s hard to compare an aluminum producer like Alcoa Inc. (NYSE: AA) to a precious metals company like Wheaton Precious Metals (NYSE: WPM) as the commodities they sell are inherently different. However, that doesn’t mean the comparison doesn’t turn up an interesting and important difference in their business models. If you are trying to determine if Alcoa or Wheaton Precious Metals is the better buy, focus in on costs.