Why would Stipe fight Ben ? <| sep |> 211 sephiroth and tifa . <| sep |> If there is a difference in price after currency change then there is a opportunity for arbitrage to buy one and sell on the other exchange for a profit . This attracts people and robots to make money off the difference and in the process it drives the prices back so that there is almost no difference after currency conversion . It ' s like a selfpolicing thing , the opportunistic algorithm traders keep the prices about equal through their attempt to profit off any difference that pops up . So if one stock goes up by 25 cents a program will probably buy one stock and sell it on the more expensive exchange . The next person will buy the lower stock at 24 c cheaper , then 22 c cheaper and before you know it both stocks are up 25 c . This all happens very fast . This is what happens for stocks on the large exchanges , if there is a problem obtaining one of the stocks or selling one for the other than a gap may exist .