The versatility of couscous is only out weighed by it's ease to cook. Take equal parts of couscous and boiling water, mix and let it sit for 5 minutes. Done. To plain couscous you can add pretty much anything; veggies, chicken, fish, legumes. You can treat it like pasta and add pesto or you can treat it like rice and add soy sauce. Couscous is the uber neutral, easy to cook carb.
1/2 cup cooked has roughly 88 calories, 17 grams of net carbs and pretty much nothing else.
Bulk organic couscous averages 75 cents per 100 grams. That may sound expensive but you really don't need much couscous to make a hearty meal. 1/4 cup (40 grams) dry = 1/2 cup cooked, which is a perfect size for lunch. Cost 30 cents per 1/2 cup serving.