I don't know how common it is, but I like carrot stew (EDIT: hutspot). 1kg carrots is around 1.30€ here, a bag of 2.5kg potatoes is around 5€, peel and cut it all, add a chunk of smoked bacon for flavor (ca. 2.50€ per piece) add water, broth, salt, a bit of pepper, maybe parsley, and just boil it all until it's soft. Onion and garlic to taste - they don't need to be fresh. Freeze-dried works just as well.

You end up with ca. 3,5 kg for 8.80€ and If you go by 500g per serving, that's 7 servings for 1,25€ each. A little more if you buy the onion and garlic fresh, but it doesn't make much of a difference both in taste and price, so I usually go with the freeze-dried stuff. If there happens to be too much broth, you can just dump a bag of mashed potato powder into the pot.

If you have a freezer, you don't need to cook everything at once - get some zip bags, fill them with the peeled / cut raw ingredients in equal parts and store it in the freezer. If you want to cook it, just dump the contents of a bag into a pot, add water & spices and boil - no need to thaw first.

I used to cook this whenever we got together for roleplaying sessions and it was my turn to host. ;) It's not difficult to cook, cheap, tasty and feeds a bunch of nerds for the evening or supper for yourself for a week.

PS: 1.00€ = ca. $1.07