This has been my experience as well. There are excellent waiters/servers at lower-end and mediocre ones at higher-end restaurants.
The same line of thought makes we wonder whether the waiter works harder to serve me a tenderloin steak than when serving a pasta dish ( at 1/3 the price) at the same restaurant.
A system where waiters are paid below minimum wage is inherently wrong, no matter how you look at it.
I tip the way "you're supposed to" but have always felt weird about the whole arrangement. I'd rather restaurants charged more and paid their staff a decent wage, leaving me to reward outstanding service, rather than having to subsidize by-default the meager pay they get.
Out of curiosity, for those who have worked in this industry, how much time does it take to take care of a party of 4, let's say? Including taking orders, co-ordinating with the kitchen (if necessary), preparing the bill, etc.