Where the waiter needs special skills (such as a knowledge of wine, for example, or those involved in the strange ritual of silver service), then I agree it's fair to reward that. However, in most cases I don't see that the skill needed to bring a plate of expensive food to the table is significantly greater than those needed to bring a burger. The food may be more complicated, but it's not as if the waiter cooked it.

The things I generally appreciate in a waiter (promptness, efficiency, friendliness) aren't, as far as I've been able to see from my fairly limited experience, correlated to the price of the meal or the poshness of the establishment. You may have a point in that customers in posh restaurants tend to be more obnoxious, though! So perhaps they deserve a bit extra for that.