Big W are selling the iPhone 6 from $858 (that's $11 less than Apple).
Assuming you can find one…
Entertainment Card holders can purchase Big W & Wish Gift Cards at 5% discount. So $850 of gift cards comes to $807.50 (plus $8 remaining). That's an everyday price of $815.50 from Big W without resorting to price matching.
Don't forget to pay with a FF/rewards points accruing credit card.
Don't forget to show your Everyday Rewards card for even more FF/rewards points.
Finally, be sure to leave the country within 60 days to claim another 10% back from TRS (that's $815.50 - $78 = $737.50 after refund). Maybe use some of those FF points you've been racking up. Don't forget to ask for a complimentary seat upgrade.