I don't know about in Vegas, but Fatburger in Denver is very pricey for what you get. Cheeseburger, fries, and a drink run almost $8. It was good, but I think I'd rather go to Fuddrucker's for that price.
My personal favorite Vegas meal for $8 is La Creperie in Paris.
The half-rack of ribs at Westward Ho isn't too bad for $5.