I guess I was thinking snacks first and foremost but cheap carbs aren't necessarily unhealthy. Protein sources are probably the most expensive and mixing in veggies is pricey on a calories/$ basis.

But rice, beans/legumes, and a lot of other basic staple foods are pretty cheap. Eggs are back under a dollar by me at least.

Not having the time/means to shop and prepare food makes sense, or if you're in a food desert and don't have much available conveniently.