Cheap Iphones in the streets

Sometimes you can get this kind of offers. Someone will try to sell you a really nice iPhone for 200 or 250 USD. These phones are inside the box, brand new. The problem is that there is a lot of problems that can happen in this transaction. 1 - you can get a clone. (not a real iPhone but look like a real one). 2 - the person can change the boxes without your notice and when you open the box you get a rock. So never go for good deals like this.