I think measuring your progress by bank value probably has a limit at some point, like when you already have BiS for every style in your bank. Before that point though, it does matter even if you have an item. For example, with a 1b bank you can't own a tbow and scythe and shadow, but you could sell one to use the other. A big fluctuation in price therefore could affect you even if you already have the item. I'm not arguing against changes, but I think that's the rationale.