Even they're skeptical, though: Their tipster isn't one of their regulars, and so they can't say with any certainty that it will come to pass.
The discount makes sense, in a way. Selling the low-end iPhone at a ridiculous price will turn it into the new Motorola RAZR. Apple would love everyone in the country to own one, I'm sure. It's not clear who will eat the discount, though -- Apple, AT&T, or Walmart -- but my guess is that it's mostly Apple. Apple has other revenue streams for the iPhone, such as the App Store and iTunes, and AT&T still has its spendy two-year contract. If this is what Apple needs to do to make this the ubiquitous handset to have, then it may be worth the cost to them.
On the other hand, as many commenters at BGR have pointed out, with ubiquity comes rejection. Suddenly, the iPhone isn't the cool status symbol to have anymore. This doesn't bother me one bit, but to some people -- for whatever reason -- it's important to them. (I have special names for those people.) Nevertheless -- will it impact sales? How much is the "hip" coefficient driving purchases?
In any event, consider this one of those situations where the Internet is writing checks that Walmart's butt might not be able to cash. But pretty sweet if it does.