That's because reselling the phones here in the US gets you only about a $20 profit per phone, but reselling it overseas will get you over $100 profit per phone
Overseas where? Iraq, Iran to detonate IED's?
A lot go to India. And no, not to detonate IEDs. There are a hundred ways to detonate IEDs. Anyone want to use a cell phone for that would not need to import hundreds from the US.
Besides, you are concerned about cell phones going to Iran, but are not concerned that F-14 parts are?