Right, we pay our waitstaff next to nothing in terms of hourly rate (it's well below minimum wage) and they make all of their money on tips. If a bill is $50 worth of food, you should tip the waiter on that, even if you got it with a Groupon that cost $25.
Waiters at higher-priced restaurants do make considerably more. Thus those restaurants are far more selective (a lot of waiters at, say, Fridays are new to the trade, not so at Mortons) and the waiters are better. Their jobs are more time-consuming too since there are more courses, wines, they're expected to be more knowledgeable about the ever changing menu, etc.
Waiters at higher-priced restaurants do make considerably more. Thus those restaurants are far more selective (a lot of waiters at, say, Fridays are new to the trade, not so at Mortons) and the waiters are better. Their jobs are more time-consuming too since there are more courses, wines, they're expected to be more knowledgeable about the ever changing menu, etc.