Commomwealth Bank of Australia has used the 4GB model of the third-generation iPod nano to compare global currencies and purchasing power in 55 countries, reports Reuters. The survey found that Brazilians pay the most ($369.61) for the device, while Hong Kong edged out the U.S. as the cheapest place ($148.12) to buy the player. Piper Jaffray analyst Gene Munster has issued a research note claiming that 10 percent of all iPhones sold in September were…