If people in countries with low wages can perform the work, why on Earth would you pay double to have high-wage people do the work? It makes no sense. Taking advantage of the differences in local pay scales is called labor arbitrage, as the employer is trading on (i.e. arbitraging) two sets of prices.
It's not just labor that can be arbitraged: currency, interest rates, risk, environmental regulations, commodities--huge swaths of the global economy can be arbitraged.
The basic idea of the global carry trade is to borrow money cheaply in a currency that's weakening and use the money to buy low-risk, high-yield assets in currencies that are gaining in relative value. It's a slam dunk arbitrage: not only does the trader earn an essentially free return (borrowing yen at 1%, for example, converting the yen to dollars and buying Treasury bonds paying 3%), but there is a bonus yield on the dollar strengthening against the yen: a two-fer return.