While brief sales on iPhones are relatively common, it's rare to see permanent price drops outside of a hardware refresh cycle. Walmart is willing to give those cuts a shot, however. Visit the company's stores from this point onward and you can pick up the 16GB iPhone 4S in its AT&T, Sprint or Verizon forms at $39 on contract, instead of $90. The 16GB iPhone 5 for those same networks is dropping to $129 from its usual $190; sorry, T-Mobile fans, you're out of the loop for now. It's not hard to understand Walmart's sudden generosity -- when the iPhone range is nearing its annual upgrade, the lower prices should keep current units moving.