The way I see it, a 50 min massage, and a meal + drinks at rockpool would cost way more than $56! Normal terms and conditions apply, like you have to be taking a QF or JQ flight the same day, only valid once, etc.
As mentioned, it's just Neil Perry 'designed' food. That said, there's some very good ones (if you were going in the next few weeks, i'd highly recommend the Fig salad starter it's amazing).
If you want a spa slot, be sure to get to the lounge at least 3 hours before your flight (ie, as soon as you can after check in opens) or earlier if you can. MEL slots fill up very very quickly, and SYD seems to be booked solid a lot of the time. The earlier the better.
You'll get a 30 minute back massage at best, as the longer treatments are reserved for those flying in F. Sometimes you will only manage a manni/peddi or a neck/shoulders massage.
Still, for the price you got it for, it's a bargain. I recommend the Taittinger with a good splash of Tanqueray No. 10