I know a couple who buy meat at the military commissary (or whatever it’s called). It’s a LOT cheaper than regular stores. I don’t know about other stuff.
Commissaries can save you quite a lot on your grocery buying. Of course, some of that savings will be reduced depending on how far you live from a commissary and how many people in the family. When my kids were younger and living at home it made more sense to shop at the commissary. For me, its a 60 mile round trip and buying only for the wife and I. So while we still go to the commissary we don’t go as often.
Only way for you to find out is drive to a commissary and check the prices.