I see where you're going, but I think even if they take a hit on the returned phones they reap a few other benefits
1. They get the best phone on the market
2. They lock in customers. Most cellphone users stay with their carriers past the 2yr agreement unless there is some mitigating reasons to drive them off.
3. They will most likely pull some att customers, who, may have purchased junk phones or even an iphone in waiting for the verizon iphone.
4. Lastly, prestige...