Nearly the same phone, right? The respective iPhone 4 smartphones for both Verizon and AT&T contain a few subtle differences in design and internal structure—namely, potential changes to the antenna to alleviate the oft-discussed "death grip" problem and a Verizon-style CDMA chip to replace the GSM functionality common to AT&T's network.

And, yet, while both phones cost for the exact same amount once you factor in all the contract finagling--$200 or $300, depending on the size of the phone, for a two-year contract with either provider—the two companies are selling the actual retail version of the iPhone 4 for completely different amounts. In this case, it's a difference of $50 for either size: the 16-gigabyte iPhone for will set you back $599 from AT&T and $649 from Verizon, and the 32-gigabyte version runs $599 and $649 respectively.

So what's the reason for the difference? It's unclear: Either Verizon is charging a little bit more because of the CDMA chip found within the iPhone 4's insides, or it's charging more simply because it can. Piper Jaffray Gene Munster estimated in January of this year that Verizon could pull in as many as nine million new iPhones this year—with up to 6.5 million of those defecting from AT&T.

While it's clear that not all of those purchasing new or jumping ship would be paying the full iPhone 4 asking cost, there's certainly a percentage that will be coughing up top-dollar for an iPhone 4. In fact, Verizon's $200 rebate plan for current smartphone owners—announced earlier this week—is itself completely based on the full retail price of the iPhone.

In the plan, Verizon has offered a $200 credit to those who activated a smartphone between November 26, 2010 and January 10, 2011. However, that's not a credit to the contract price—no, the $200 comes in the form of a Visa gift card that's sent after one buys the iPhone 4 at full retail price. Which, as we've noted, translates into an extra $50 in Verizon's coffer compared to the "normal" iPhone 4 cost.

Analysts have also noted that Verizon's iPhone 4 might itself cost less to make than AT&T's.

"A combination of falling component prices and potentially a bit of simplification to the radio means our original $200 iPhone4/32GB hardware BOM cost might be closer to $175 for Verizon's version of the product," said David Carey, a vice president at UBM TechInsights, in an interview with EE Times.