That savingfortravel site is helpful but it is a bit high. I think bungle girl told me it was about 1/3 too high. Anyway check it against what you think it would be suitable to budget in your own country.
That said, its not a big problem to over budget. And then on the other hand, if you over budget too much you find you start to waste money even. So if you do find you have more than you think you might need, tighten you budget and use the excess later when there is something worthwhile to splurge on.
Certainly in Australia to do touristic things - like a reef trip or go up the top of the harbour bridge etc these cost a lot of money. Or sailing in teh whitsundays. So save up for those things. In Australia it is worth cooking your own food in the backpacker joints you stay in because so many food places are over priced and often as not disappointing food. If you want to splurge on good food, go somewhere like Tetsuyas in Sydney or the Nautilus in Port Douglas and have a really special meal or two. Also shopping at woolworths is cheaper than any other supermarket.