I'm not even sure where I read about this idea this week. I tend to read a lot of books and articles on food, homesteading stuff, food economics and such.
I can eat pretty darn well on $35-40/week at a supermarket and do far better then most people (though an extra $10 can let you buy more local stuff, and the garden in the summer really helps!), though I still have a lot to learn. The lack of skills in preparing food and how to shop in this country is tragic...what I see being bought on Food Stamps far too often makes me shake my head (especially if it was a week I was really working to meet the $35 limit).
Something that stunned me I never knew before:
You don't need "Microwave" popcorn to microwave popcorn.
You just need popcorn, and a paper lunch bag:
Threw in a bit of popcorn and couple dashes of salt. Roll down top of bag, nuked on Popcorn setting (3:30 seconds). Decided after I tried it to take a tiny plastic cup and nuke a pad of butter for 20 seconds to pour over the top...not much at all, maybe what I'd use on a single slice of toast.
So easy any kid who can nuke packaged Microwave popcorn can do this. Don't see any reason you couldn't pre-measure and salt the popcorn for your kids to throw in for snacks if they have a hard time judging how much to put in the bag on their own.
1) The popcorn is a little cheaper, and my guess is careful shopping would let you find a really good bargain, but that's not where you save the big bucks, that's the next reason.
2) You're not stuck with the single size of Microwave popcorn. Just make up what you want (and need!) which is probably 1/4 to 1/3rd as much as a microwave pack. Watching a movie with folks? Pour it in a bowl and re-use the bag to make more later so you're not munching on cold popcorn half way into the movie.
That's saving money AND eating less -- you're not either over eating to finish the bag the companies make for you, or throwing out half a bag of popped corn.
3) You're not eating that nasty artificial butter stuff.