On average, each serving team is assigned 18 guests per seating. Works out to 36 guests per cruise.
I have also heard from many different servers that about 20% don't tip at all. That's why you see so many empty tables on Friday night.
I've spoken with servers who were college professors, engineers and other white collar jobs but came to
DCL because they could make more money and support their families back home.
These folks work hard for their money and spend six months at a time away from their families. I think they earn every penny.