i think the real question you are getting at is: How much would it cost to live and eat like a local, not an expat?
A pack of homemade tortillas is about $1.25 bzd for 4. Eggs range from $.10 per to $.30 per egg based on whatever the menonites feel they should charge at any given time...
rice, beans, and the like are a couple dollars a pound, let's say $3 bzd as a good jumping off point.
Net net: if you eat completely local, you can expect to spend about $75 bzd a week on food per person. I eat like a local expat, and i spend about twice that... cheese is a killer to the budget, but i cannot live without cheese.