I know it is Shoppingsquare … and it is a grey market phone … but still the cheapest i have seen around …
$711 is still a lot of money and the new iPhone 6 is around the corner soon … which might equate to even better price on the old one (as usual).
Be aware of any warranty issues when you buy a grey market phone … I personally doubt that Apple would let you down but you never know …
Apple USA, or Apple HONG KONG, will not let you down as far as the ONE YEAR Warranty 'goes'. However, you will have to take the 'phone back there yourself (or have a trusted friend/relative there to take it for you - after you get it there by a costly courier).
You could of course trust ShoppingSquare to fix it or to return it to USA/HK for you - might take some time.
Just 'weigh-up' if the saving you make justifies the risk.