Gears 3 - $16
Gears 2 - preowned - $9
Gears Judgement - $30
Judgement comes with a code to redeem the full original Gears game + 2 days Gold membership. Also comes with a pretty large pre-release promo poster and a code to get the Web Lancer Skin gets emailed to you too.
Shipping is $7.90 Aus-wide from NZ. Works out to be about $15 per game + a couple of extra goodies.