The price difference at Bitfinex compared to other exchanges is roughly $110 at press time. The large spread has been ongoing for the past five days and began when the exchange halted fiat withdrawals. The price difference and suspended withdrawals have quite a few skeptics concerned the community could once again revisit the bad memories of the Mt Gox fiasco in the past.
read more:https://news.bitcoin.com/great-price-divide-widens-bitcoins-2017-rise/
You just have to avoid exchanges like bitfinex.
The reason why prices tend to converge at exchanges is because people arbitrage if the prices are different. With Bitfinex, you can't withdraw fiat and there are no arbitrage opportunities.