A few trips to Morton's steakhouse left me wondering - a place like
that has decent volume and fairly high check averages.
 Do the waitstaff there make good money?  If so, how much for a
typical eight-hour shift?

Here are a couple of pages to help you explore on your own.

http://www.tipping.org/TopPage.shtml
http://www.ontherail.com/weeds/index.asp

A close friend of mine worked at an upscale restaurant for several
years. She did okay, but you might be surprised to learn that people
who dine at fancy eateries are often cheapskates. It wasn't uncommon
for my friend to serve $200 worth of food and drink to a table of
four, and receive a $5 or $10 tip at the end of the evening.

I pulled in $20/hr at a divy mexican restaurant in tips, but that was
just the shock value of a white person in virginia who spoke spanish.

Most New Yorkers top 15-20%.  Bartenders make even better money.

grrr. "tip", not "top"