You are right, it is tough times atm, cost of living has skyrocketed with no relief in sight for the middle incomes, I've even delayed my retirement for a year or two so I can secure more funds.
Your cost of $511 is certainly high for a couple's weekly groceries bill, you need to try different shops for different discounts & specials, try shopping in stores such as "NQR"
https://nqr.com.au/ for better deals, as others stated, bulk shopping is another way to save.