Prices vary hugely from place to place so it's hard to get too specific in advice. But generally, if most of your spending is at the greengrocer's, butcher's and fishmonger's, you're probably doing alright in both health and finances.
I got tired of all the arguing about what to have for dinner and did we have the ingredients and who'd go to the shops and all that, so I just made a menu.
Monday - Chilli - ingredients carrot, celery, onions, garlic, zucchini, minced beef, tinned kidney beans, tinned tomatoes, spice mix
Tuesday - Soup - usually pumpkin/vegie - carrot, celery, onions, garlic, capsicum, butternut pumpkin, potatoes
Wednesday - Steak, chicken schnitzel or salmon and salad with fruit salad
Thursday - Japanese curry - onions, potatoes, fried tofu, japanese curry mix
Friday - Roast - cycle through chicken, beef, lamb and lasagna, except for the lasagna accompany with salad and roast potatoes
Saturday - Pasta - usually a sauce with same ingredients as chilli except no beans or spice
Sunday - wife's choice, ie this is the day she cooks.
Lunches during the week, I just make extra portions of dinner and that gets reheated the next day. Breakfast is weetbix, oats or eggs.
We get some plain biscuits for snacks, and go through stacks of milk.
So you see a lot of ingredients in common through all of that. This means I just have a stocklist, a couple of times a week I go through fridge and pantry and see what we're short of. Like, "Should be 12 litres of milk, we have 4, get 8. Should be 3 zucchinis, we have none, get 3." And so on.
I allow $20 for treats, like last Friday I picked up smoked salmon, cream cheese and bagels.
I change the menu each three months to allow for seasonal fruit and vegies. We just have a normal fridge with a small freezer section on top. As two adults, a 5yo and 1yo, we spend $120-$130pw. The variation is mostly from the vegies, like zucchini might be $3/kg or $6/kg, etc.
If anyone doesn't want what's on the menu, "Great! What are you making for dinner?" And then it turns out they don't mind having pasta again so much after all.
In this way we have more or less consistent nutrition and grocery price. It takes a fair bit of work in shopping and cooking, which not everyone has time for. But that's the equation we all face: money, or time, you must spent at least one of them.
I think the main thing is to have some sort of plan. Whether it's a good or bad plan is less important than it's a plan. And then if the results aren't what you want - not tasty enough, too expensive, not enough nutrition, "but can't we have popcorn?" or whatever - then you change something. And eventually you end up where you want to be.