ken..
i tried responding yesterday but when i previewed the post i lost it. I'm not yet facile in cyber world. Regardless of the culture you are living in, basic food costs certainly can be reduced to a manageable budget. 1st thing. Get rid of sugar, all refined flours, any thing that has a name of more than 8 letters. 2nd. you/they must change the mind set. One must control the food sources for both quality of nutritional value and containing costs.
Most of what you're asking can easily be accessed via computer. the key is to buy in bulk; do most of your own cooking; freeze and store accordingly; remember, in a food budget, spending 50 pesos a day for, what ever, vs. saving that same 50 pesos in a bank will return to the family unit over 500,000. pesos in 15 years.(@ 25%) when shopping shop with mix and match in mind. Beans, rice, yucca, plantainos, etc. are all good foods but they are incomplete as protein.they lack the basic amino acids to complete them. Amazing how all those ignorant, backward 3rd world peoples have worked this out by themselfs by mixing the correct foods to complete them and gain the most. No Mcdonalds! or fast food. Hate to say it but no breads.
Is there anything cheaper than chicken, fish, vegetables, fruits purchased at an INESPRE as PIB suggested, sauces made by hand instead of by can, powdered milk is of the highest quality protein and costs a max of 10 cents per gram. Have them give up fried, deep fried, battered, buttered, coated, foods.
I suspect this is not what you were looking for as an answer and I apoligize if I give offense. None intended. It ain't easy. But as you go on it gets better. You're stronger, healthier, eating a whole lot better than your amigos and will have more money in your budget. John