When buying/selling substances, the price has to be in the price range to the Grand Exchange. However, a company has the RS gold choice to how much of a product a individual could purchase. For example, a mining cimpany can sell 100 adamant ores at 110k. There is absolutely no arbitrary set of a product that a person can purchase. In this manner, the company controls just how much they produce.
That is it. I know this is similiar to the Grand Excahnge, but it gives individuals an opportunity to make experience, in addition to some cash. I really do beleive RWT is covered too. Whichever priest you decide on, they'll inform you Father Uhrney in the restless ghost pursuit has found a particular"package" and cheap RuneScape gold they want you to pick this up. Upon entering dad uhrney's house, you fill find he is now where to be found!