I was just looking at the MYER website and they have a Buy more & save deal on LEGO
Buy more & save
50% off the second item of the original price, when you purchase 2 items across Toys, selected Lego, Costumes, Kids Art & Craft, Puzzles and Books.
Discount online will be distributed across products qualified for offer within the order. Purchased in one transaction. Not in conjunction with any other offer. Excludes: Clearance, Board & Card Games, and selected LEGO ranges (Creator Expert, Creator Black Packaging, Ideas, 71043 Harry Potter Hogwarts Castle, 76139 Batmobile and 42115 Lamborghini Sian FKP 37)
Usually this means that you can get maximum 25% off if you purchase 2 items at the same price, but I found it ends up in a blanket 25% off the RRP.
EG adding the three items below
$29.99 down from RRP $39.99 (NB sale price $34.99) Harry Potter Hogwarts Moment: Transfiguration Class 76382
$29.99 down from RRP $39.99 (NB sale price $34.99) Harry Potter Hogwarts Moment: Potions Class 76383
$262.50 down from RRP $349.99 Nintendo Entertainment System 71374
I'm sure you can get creative with your combinations to get a good deal.