These three companies pack market-beating investment potential at fire-sale prices.The global economy is vast, with trillions of dollars constantly flowing back and forth. Facilitating all those transactions is big business, too. The global payments market is worth an estimated $2.6 trillion and could grow to nearly$5 trillion by the decade's end. You don't need to look hard to find an investment opportunity here.Naturally, such a big industry attracts a lot of attention. But you don't need to find the nex ...