>Operating a commissary in a prison is more complex than a local convenience store

Why so? Here they just got a few pallets of normal grocery store stuff and mostly used inmate labor to run it.

Really simple and costs essentially nothing to operate, especially since they don't have to be open every day.

The only complexity comes from potentially transporting the inmates to the commissary, but that's not a particularly efficient way to do it when you can just give inmates paper "menus" where they can just fill in their orders and have them brought to their cell blocks.