Considering the lifespan of your average restaurant, I doubt the majority are making huge bucks.
The ones that do well over the long term usually have a staff that likes it there because they make buckets in tips. And by definition, the restaurant that's doing well has lots of customers, so they're obviously pretty happy with the whole cost/benefit thing as well.
The restaurant business is so competitive that any place that is "screwing both the waiter and customer" will go out of business fast.
It goes unnoticed by the customer, you see, because the customer is paying the waiter the wages that keeps the waiter happy and the customer is desensitized because the custom has been conditioned into the culture through implication of necessity and presumption of decorum. 