The Best Things In Life Are Free... Why Aren't Groceries?

I was talking to a lady yesterday about grocery shopping, and she could remember a time--approximately 40 years ago--when a week's worth of groceries for two people cost $35. I guess if you really got down to the nitty gritty, you could eat for a week on $35--if you had to. But between three meals and three snacks a day (which everyone should do and I have to do, according to my doctors), I find it quite hard to have a $35 grocery budget.
I came across some ideas a while ago on how to keep your grocery bill to a minimum. Make a list and a budget and stick to it; go in the store with a certain amount of cash and leave all other forms of payment (credit, debit, checks) in the car or at home; give yourself a time limit & try to "beat the clock" every time you go shopping...
I think the cash idea is the most effective (I wish I had done it when I went shopping earlier!). If you only have $75 in cash, then that's that. You might have to put a few things back, or just plan/budget better, but at least you know you won't go over your spending limit. And after going shopping a few times with that mindset, I assume it would have to get easier.
Overall, I think grocery prices are insane. Milk is almost $4 a gallon, and I just spent $6.49 on grapes! It seems the healthier you want to eat, the more expensive it is. It's no wonder America is home to so many obese people. Maybe if healthy foods were cheaper and junk foods were expensive, we could all lead healthier, happier, more affordable lives. But now, what sense would that make?
I know there's more to it than that, but wouldn't it be nice if you could get a week's worth of groceries for $35? $70 for a family of four?
What are your tips on saving money when grocery shopping?