Okay, this seems like the same thing I guess? If it is the same thing how is this easier than what I've done already or more accurate? Would you intend to use a different graph for each item? I think that would be a little confusing to figure out for the majority of users. Plus, I'm not sure if that method can factor in rarity of an item that I am basing off the amount of qi that the general public has. Wouldn't this show that price of a Void Force is constantly going down because it's not really being bought often, if it is based on trends?

I'm open to new methods mathematically that may be easier than the way I've used in the example but I don't know about showing everyone a chart for each item, or even the result of the chart since it cannot judge things by it's rarity. Plus, this chart seems more useful if you are wanting to look over long periods of time which isn't the case. The way I'm proposing would update a price range all the time simply based on the math of for how much people are buying and selling and how often they are on certain prices.