The exchange rate is almost identical through all exchanges. Have been studying the market for a while, the slippage between exchanges barely last more than 5 minutes.
Apparently you didn't study it last week when Coinbase was $20-$50 different from BTC-E for 5 days.
Are you sure BTC-E wasn't the outlier? That's what I've seen in the past.
I've been watching the spread between exchanges for a long time at https://cointhink.com/arbitrage/btc:usd and BTC-E is nearly always 'away' from the rest of the markets by 5% or more, and always less than the others. I assume there are significant hurdles to getting USD in or out of this Bulgarian exchange.
I'm not sure it makes sense to talk about outliers when there are so few major exchanges.