Physically identical things are often sold for different prices, usually because of accompanying conditions that are quite different. If a camera store sells a particular make and model of camera for $300 and the discount house sells it for $280, it may still pay to go to the camera store where another make and model of camera is available for $250 that does what you want to do just as well or better. If the camera store’s larger selection and more knowledgeable sales staff enables you to buy only what meets your own needs, there may be financial savings there, as well as better advice on operating the camera, even if the discount house charges a lower price for each particular camera that both stores carry. The point here is not to claim that it is generally better or generally worse to buy cameras at a camera store or at a discount house. Instead, the point is that what is being sold in the two places is not the same, even when the cameras themselves are physically identical. The ...