$5 is certainly a challenge here in Manhattan where everything is more expensive... Also, lots of dishes that I make use things like fish sauce or whatever which can't be bought in small quantities, except for Red Boat, which is extraordinarily expensive and I haven't had the nerve to pull the trigger on it yet. But even still, my $3/liter of fish sauce works out to like $.001 per serving. Also, many of the curries I make may cost $20 worth of ingredients (many of them have to come from who knows where, and there isn't a lot of competition for it) but that batch of curry is good for usually 4 meals for 2 people (so 8 servings) - I can't justify doing all work for 1 meal.
While I understand weinoo's philosophy, I looked at the OP as a challenge of how to eat well for very little money, not just to eat for sustenance. I would hardly compare beef stroganoff to rice and beans. I was pretty impressed he could pull off a stroganoff for $5.
Exactly munchymom - I think that's a great idea!