Usually you have to pay postage of around $15 or thereabouts, so making that a deal breaker (because they usually send out a physical prepaid card). But I phoned up and they said these are electronically delivered so no postage charge, the code is emailed and its all legit (or so they tell me). Same price in their sister stores as well:
http://www.megabuy.com.au/microsoft-xbox-live-prepaid-24-mon…
http://www.wacomputers.com.au/microsoft-xbox-live-prepaid-24…
http://www.tech4u.com.au/microsoft-xbox-live-prepaid-24-mont…
FYI - just found out 2.5% charge for credit card and paypal … no charge for bank deposit though
"Usually you have to pay postage of around $15 or thereabouts"
It should be $2 to post a piece of paper in an envelope around Australia. However its digital codes, why the need for posting?