Here's a reasonable deal from Jumbo Pets for people with large breed puppies -
The 15kg Hill's range is on sale for $89.95 a bag ($10 off as usually sell for $98.95). Buying two of these will also qualify you for another $10 discount using their voucher, saving you a total of $30 Jumbo Pets' prices.
2x 15kg of Hills Science Diet Large Breed Puppy food for example would work out at a total of $167.90 ($83.95 a bag) if you collect it from store or $174.85 delivered.
On this specific food you're saving at least 25% off compared to prices elsewhere, which range between $225 and $280 for two bags delivered from what I could find online (Petbarn, Direct Pet Supplies, Claws n' Paws, My Pet Warehouse, Petstock, etc.).
My 8 month old German Shepherd puppy finishes a 15kg bag in just about a month, so looking at it another way in my case it's like getting two weeks supply for free.