Oh, gosh. It varies every week, but I am generally very routine about what I buy so I know how it all evens out.
One of the big staples is eggs. We just recently got a Ruler Foods in town. They sell a dozen large eggs for 59 cents. I buy at least two dozen eggs every week, sometimes four dozen. Cheese is also cheap there, less than two dollars for 8 ounces. Before we had one, I bought cheese at other grocery stores only when it was on sale $2 for 8 ounces.
Meat I shop on sale and on sale only. Four pound bags of chicken for $7-9 depending on how good the sale is. Pork for $2 a pound or less. Bacon is $2-3 a pound.
I buy apples just about every week, $1.79 a pound is the normal price for Granny Smith (my fave) right now - I buy 3-5 at a time so I pay about $2-3 for the bag. I will sometimes buy berries if they are on sale, other times if I really want some (and it's on sale) I might buy a frozen bag. I just bought raspberries last week because they were 11 for $10. Bananas I buy when they are discount because I like a brown banana anyway, and they are seriously dirt cheap when I buy them. Like 29 cents a pound and that's 2-3 bananas? They freeze great too so I will sometimes buy several bunches and freeze them.
For other produce I buy sweet potatoes, sometimes I buy white potatoes, 79-99 cents a pound and the average is about half a pound. The rest of produce I will buy off the discount produce rack, kinda whatever is there that I like, and I'll clean it, process it, and chuck it in my freezer if I don't eat it right away.
I have changed my eating habits a bit but I buy a jar of natural peanut butter about every other week-ish, that's $2.79.
So let's say I buy two dozen eggs ($1.18), a block of cheese ($2) a package of chicken ($9), two pounds of pork ($4), 3 apples ($1.79), a couple sweet potatoes ($1), a bunch of overripe bananas (70 cents), and a jar of peanut butter ($2.79) $22.46 (and I can tell you I don't actually buy chicken and/or pork every week!)
Breakfast would be eggs, cheese, and pork, or banana and egg "cake."
Lunch would be an apple and peanut butter, or a sweet potato, or maybe some leftover protein from dinner.
Dinner would be chicken, pork, sometimes an omelet of some kind.
I've been careful and lately I've been able to do one non-grocery store shopping week every month. But like I said, by the end of that week I legit have NOTHING left to eat (or it's stuff like I have a bag of almonds LOL.)
About every three months I go to Sam's Club with my mom and will buy nuts and dried fruit. It's about $40-60 when I go depending on how much I bought - one time I bought pecans about six months ago (and have used them all of twice.) So that puts me still at $20/week to balance out those "I didn't shop this week" weeks (which is really why I started pushing those non-shopping weeks.)
It all runs down to just being very routine with what I eat. And I waste absolutely nothing. The freezer is my friend.
ETA: Despite being paleo/primal/clean/whatever, I don't buy a **** thing organic/grass-fed/et cetera. I cannot afford it. I get nervous when I make those expensive trips to Sam's Club hence my "I think I'm going to not go grocery shopping this week..." reaction.