Apple started selling unlocked iPhones on Tuesday in the US that allows owners to switch carriers when travelling. This is good news for US users but what does this mean for Aussies who have to buy unlocked iPhones at $300 Australian dollars more than their US counterparts? This means that resourceful Australians can buy the cheaper US version of the iPhone and use it in Australia.

Previously US iPhones were locked to the AT&T network or T-Mobile USA which prevented them being used by other users in other countries. US iPhone users had to be content with paying AT&T's roaming charges when they left the country. You could technically get an unlocked iPhone but only if you want to deal with hackers to unlock it. Now that's all changed this Tuesday when Apple started selling unlocked iPhones for general use.

Travelling Aussies in the US can now pick up an unlocked iPhone 4 and put your own preferred SIM card and use it in Australia and around the world. US iPhones only cost $649 and $749 for the 16 Gb and 32 Gb phones respectively. The same phones cost $859 and $999 in Australian dollars in the Australian Apple store. If you buy an iPhone outside the country, Apple will still cover your device through their international warranty.

The only downside is that you'll have to pay the local sales tax and there's no sales tax refund system for visitors. If you want to avoid paying sales tax you can buy your iPhone in these states without sales tax: Alaska, Delaware, Montana, New Hampshire and Oregon. California has the highest sales tax in the US with 10.75 city sales tax, so avoid purchasing your devices there. New York City has a 4 percent sales state tax and 8.875 city sales tax.

If you're stuck in Australia you can still buy an unlocked iPhone 4 by importing the device via PriceUSA. The Australian based company will buy the items for you, sales tax free and ship them to Australia. There's still shipping costs and the 5% fee PriceUSA adds but overall you would still save money buying the iPhone this way.