I'm a little confused as to how they handle different types of products under an SKU. For example, an iPhone with a short, abused life is going to carry a diff

I'm a little confused as to how they handle different types of products under an SKU. For example, an iPhone with a short, abused life is going to carry a different market price than a nearly new one. Or have I misunderstood the site? edit: It seems they have quality categories when adding a product but they still seem discrete.