Lego: plastic crack. Once you start, there is no stop.
Try shopforme they are based in Melbourne and usually are 20% cheaper than retail (about the same prices as Big W or Kmart sale prices) and get stock in earlier than brick and mortar stores.
You usually have to be fairly quick for the more popular sets as once their stock gets low the prices do increase.
Ever since lego banned amazon and Barnes and noble etc from shipping overseas it's getting more expensive. If you aren't massively into the mini figures but want just the sets it does make it easier on eBay and bricklink as there are a massive amount of sellers who pull out the minifigs and on sell the actual construction part.