I suspect you are not visiting actual grocery stores, but convenience stores, which often have wildly inflated pricing and poor signage to hide that pricing. These are often named things like "Kings Wharf Supermarket" (actual example which I will not dignify with a link), but supermarkets they're not. Add the exact address of the last shop you visited in a comment if you want to confirm.
Look for the nearest Coles, Woolworths, Aldi, or IGA instead, and you will find all prices very clearly labeled, plus often half or less of what the convenience store wants:
Obviously there are not so many of these in the Sydney city centre, because they're large and need a lot of expensive real estate, but you can find one within a few blocks if you use the store locators. For example, this large Woolies is right next to Town Hall.