I guess it's based on gox? Why would you do that?
Gox is the legacy price, and even though noone wants to admit it, Gox still drives the market in a large way.
Gox does drive the market but only with a smaller ratio of effect now. Yesterday gox price was under half of Bitstamp price. Even though it affects the price, it does not actually represent the price of bitcoin. If I want to buy a bitcoin right now and use it at a merchant or if I want to sell a bitcoin and receive cash right now, it is going to be based on Bitstamp price. The actual mtgox price is meaningless. Nobody actually thinks bitcoins are worth $300 now.