Just the other day I had a DD, fries and shake for about $6.50. For $5 you can probably get the Cheeseburger meal.
When we go to In-n-Out as a family (2 adults, 3 kids under 5), we spend about $13, but we don't get soft drinks - just water. I think the only fast food place that can beat that price is Taco Bell. And in-n-out beats any fast food place in quality, cleanliness of the restaurant, and friendliness of the staff.