They are right now but this isn't always the case. For example you can see just from that page that in the past 24h, Kraken reached a low of 1025 while Bitstamp only reached a low of 1118, a difference of 9%. If at that low, you'd bought BTC on Kraken and sold BTC on Bitstamp, you would have made that 9% difference.
This is the point of the strategy. Whenever they diverge for whatever reason, assume it's temporary and that they'll reconverge. Make money converging them.
This is the point of the strategy. Whenever they diverge for whatever reason, assume it's temporary and that they'll reconverge. Make money converging them.