Like I said. WRT the 3G model. If purchased from Apple, they charge no restocking fee for the iPhone and it has a 14 day return policy. If purchased from AT&T they ALWAYS charge 10% restocking fee but have a 30 day return policy.
http://www.apple.com/legal/sales_policies/retail_us.html
iPhone Sales Policies
The purchase and use of an iPhone is subject to terms and conditions found at:
http://www.apple.com/legal/sla/ and
http://www.apple.com/legal/warranty/. In addition, by making this purchase, you expressly acknowledge that:
oA minimum new two-year wireless service plan with AT&T is required to activate all iPhone features, including iPod features. Wireless service for iPhone is solely provided by and is the responsibility of AT&T.
oThe Apple Online and Retail Stores sell iPhone for end-user customers only. iPhone may not be purchased for resale.
oApple reserves the right, in its sole discretion, to refuse or cancel any order and to limit order quantity. Apple may require additional qualifying information prior to accepting or processing any order.
oiPhone may not be purchased for export outside of the United States, either directly or indirectly.
oMaking unauthorized modifications to the software on an iPhone violates the iPhone software license agreement, and the inability to use iPhone due to unauthorized software modifications is not covered under warranty.
oiPhone purchases are limited to five iPhones per customer and must be purchased with a Credit Card, Debit Card or Gift Card.
o
No restocking fee will be assessed on iPhones returned within the 14-day return period.
EDIT: Since every iPhone is "preopened" and activated the "if opened" rule doesn't apply.
The receipt should have that information.
Apple's normal return policy is that an item can be returned within 14 days of purchase. If the item is an iPod/iPhone/Mac and it's been opened, then there's a 10% restock fee.
Apple will sometimes waive the return fee for new product launches. The original iPhone wasn't charged a restock fee for the first few weeks after its launch. After that, returns were charged a 10% restock fee.