Each exchange has its own circumstances that are reflected on the price. For example, it used to be difficult to get fiat into BTC-e, hence the price there was

Each exchange has its own circumstances that are reflected on the price. For example, it used to be difficult to get fiat into BTC-e, hence the price there was lower than the average (sell your BTC cheap now, or wait until someone wants to buy at the average price). To say that mtgox was manipulating the prices is an extraordinary claim and requires extraordinary proof, which you don't seem to have. A better explanation would be that they had problems with fiat withdrawals, probably due to ridiculous regulations and bureaucracy problems like the ones they suffered in the US, therefore the price was higher than the average (wait for your fiat, or get your expensive BTC today).