Where is the cheapest place to get an iPhone?

I want an iPhone 4 or 4S with no contract preferably locked and for AT&T I will buy a refurbished one. I'm looking for under $300

Look on Craigslist

For more detail- http://www.directphoneshop.co.uk/

You can Go and check online. The online store offers great deals and less price than physical retail store.