How do retail forex brokers make their profit with the kind of leverage they give to customers? -

The same way any other broker does: by a spread between the price collected from the buyer and the price paid to the seller. The leverage has absolutely nothing to do with it. They make their money with the spread...that is, the difference between what they buy the shares from the seller and what they sell it to the buyer...If you want to learn more about Forex trading, check out this site: http://www.forexvendors.com. It provides comprehensive information regarding the Forex.