Zybez Runescape Help has been keeping track of prices in Runescape for a long time (years!) and now, after the GE update that fixed the prices for everything, Jagex saw fit to copy Zybez's idea about having a price database to allow visitors to search for and see the prices for everything from pickaxes to mithril chain mail armor. Since the market isn't totally static, prices do change as demand goes up and down, so, Jagex has also copied Zybez's idea of graphing out the prices so people can see trends the same way they see trends for stocks on the stockmarket websites.
I'm not saying that copying of this idea is wrong. Jagex has "copied" many ideas before, and I'm glad they have. I call it "using" ideas, rather than copying them. By using an idea already invented, Jagex is simply providing for players the same service that Zybez had provided - in the end, from the player's point of view, nothing has changed. And since Zybez's main aim is to provide players with useful tools, nothing has changed there either. The players are getting the useful too - albeit from another website, but still, motive achieved.
I always come up with ways to tweak (not always 'improve', but at least tweak) ideas. So, how do I 'tweak' this one? Ok: once the prices are graphed out, find some trends beyond the one item. So, how about find trends between different items. i.e. the price of mithril ore went up, and so did the prices of mithril plate, and mithril legs. Also, then, it'd be easier to find dependencies. If two things are closely patterned, they must be dependent on each other or at least related somewhat closely.