Edit ******* I'm not sure who said they spend $30 or $40 a WEEK on diapers, but that's close to what I spend A MONTH on diapers. If you are spending more than $50 A MONTH on diapers, you are buying them at the wrong store and in the wrong quantity. Seriously, these websites and stores try to make you think their diapers are so cheap...and they are not!! I buy boxes of Luvs at Target for $16 apiece and they come with 80-108 diapers, depending on what size you are buying. Three boxes a month (which is about 300 a month, approx) gives you ten diapers a day...that's enough, right? :)
We are a family of four...I have a six year old and an eight month old, and a husband with a very healthy appetite...and our monthly food budget is under $600.
If you think about it, $20 a week adds up to $80-$100 a month...just for pizza. We are on a tight budget, and we could never afford to do that. Maybe twice a month we get Papa Murphy's (take and bake) and we maybe spend $7 each time, or less with a coupon...or get your pizza on a deal day, where they're doing two mediums for $5 each, for example.
You also should evaluate if you are buying things you don't necessarily need, food wise...if you want to cut the budget. Condiments, sauces, and extra "flavorings" really add up, money wise, and aren't healthy...I've tried to cut back on them (but it's hard because my husband likes a lot of sauce. :)
Also, as far as diapers go...really, Luvs are the best deal. I'm not sure what you use, but what you should do is take the price of the box and divide it by how many diapers there are, and see what your "price per diaper" is. This can range anywhere from 16 cents to almost 30 cents, depending on what brand and what size package you are buying. I buy all the diapers I need each month for under $45 dollars...and sometimes, when the leftovers add up, I only have to buy two jumbo boxes for around $30.
I have tons more grocery tips that I won't bore everyone with...I mean, I feed my family well, three meals a day plus drinks, snacks, treats, baked goods, etc...for under $600. And I don't necessarily buy a lot of generic and I never shop at the warehouse places...I've just (out of necessity) had to figure out tricks over the last six years. If you want more, just give me a mail!
Good luck!