There were a number of answers, but if you actually work out the math, outside of big jumps where one exchange may be moving too fast for people doing arbitrage

There were a number of answers, but if you actually work out the math, outside of big jumps where one exchange may be moving too fast for people doing arbitrage, with all the fees and transfer costs, the prices work out to be about the same. So, BTC-E has a 1% fee, plus whatever cost it took you to do the International Wire Transfer (say $35 bucks). That already gets you to ~$900. So, you get into Gox and sell. Well, that's 2200 JPY, you have to pay for the wire, $920, plus your bank probably charges you $20 for receiving a wire, $940... and that's before the 4 weeks+ it takes for Gox to get you your money + the trading fees. It may look like there's room for arbitrage but the price differences, for the most part, do take all costs into effect. (PS Yes, I know the wire transfer fees can be lowered in terms of percentage of the cost by transferring more money at once; it's just a simple illustrative example.)