No, it's not. The Mt. Gox price is disconnected entirely from other exchanges due to the inability to withdrawal either Bitcoin or dollars, and the uncertainty over MtGox's solvency.

People on MtGox are effectively trading GoxDollars for GoxCoins. Someone setup https://www.bitcoinbuilder.com/ to trade GoxCoins for Bitcoins.

No, Mt. Gox is selling Bitcoins that you will never be able to withdraw for $150 USD. Coinbase is currently listing a buy price of $611.21.