i could spend $150 per week easily, thats not including meat (which dp's mate buys on our behalf from his families butcher )
BUT there is always something that we need to buy mid-week.

also, things like toiletries/nappies/washing powder seem to run out in the same week, so thats bumps up the total.

whenever we come into some money (ie. ruddy bonuses/tax returns/centrelink advance payments etc) i do a 'stock up' shop... where i buy one or two of everything we need/use. and that lightens the weekly load, and i can grab things on special as they come up.. rather than running out and 'needing' everything IYKWIM.

the only thing i can suggest is, if you dont already do so, is make a meal plan/list including everything you will need to buy. so rather than think 'ill grab this this and this while you're at the supermarket. make a note that for the entire week you will need 1 box of salada biscuits, 4 loaves of bread, 4/6/10pk of tortillas (if you get my drift) rather than have excess that gets thrown out.