Sales, Coupons, Spending Limits for Items
We have maintained a near constant monthly dollar expense on food, even though our income has gone up quite a bit in 28 years of marriage. The trick is to buy almost everything on sale, with coupons. The sales rotate from week to week, so if you can plan ahead and/or store things, you will always have plenty when it is needed. In fact, we have so much dry goods, we had to build extra shelving in the basement for it - we call it the vault. We also have a freezer for meat.
You also need to decide on limits for the price you are willing to pay for certain items you use a lot. Boneless, skinless chicken breast is a $2 per pound item in our household. If it is more that, no go, if it is less, we can stock up. Cereal is $1.50 per box after coupons - YES this can be done and I generally have 20+ boxes of name-brand cereal on hand at any given time. Milk is $2 per gallon after any deals.
BTW, our monthly dollar limit on food is $300. We RARELY reach that limit, we have four in the family plus a cat, and we eat well. We are earning a lot now compared to when we started out, we have no mortgage or other loans, and we still shop this way!