Agree on eating much less meat and dairy to save. I found that buying at MOM's, I ended up spending about the same as my grocery trips to the regular grocery store. If I buy my grains etc in bulk it certainly reduces the cost. Also, less inclined to buy packaged organic cookies and those type products than I would be to just throw a few treats into my cart at the standard grocery store. My husband and I can make it a full week on all organic food from MOM's for about $150. Everyone's budget certainly varies but that includes food to make ourselves packed lunches, so it certainly feels like a good deal when we consider that it is all organic and unprocessed. Trader Joe's also seems to be a good value for organic fruits and some veggies from my experience.
I pretty much could have written this. I agree that (a) to save, cut meat and dairy way, way back, and (b) cut out all processed foods (or as near to all as you can). It's the stuff that comes in boxes, cellophane bags, and cans that kills you. (Your budget, anyway, though it's none too good for your health either.) Cut that stuff, and you'll be able to afford the produce, grains, beans, and a modest amount of meat.
If $600/month for a family, with work lunches, is too steep and you're trying to do it for half that, well, you're going to have some problems. (Though I'd think you'd run into those problems in the regular grocery store too. Meat and dairy aside, organic's not THAT much more expensive.)
If you want to eat as much meat as you want on $75/week, can't help you. You're in Smithfield/Oscar Meyer/factory farm territory.