OK, I borrowed an old bathroom scale from the inlaws and it's 30# for complete 18" rear wheel. This includes the sprocket, sprocket carrier, and the complete brake carrier, as well as the axle and spacers, but no tire or tube.
More accurate numbers are available but these are close.
The same scale showed the 90's 750 Nighthawk wheel I'll be using on my K3 to weigh in at 35# complete with all of the above items with the tire mounted.
So maybe an easy 5 or 6 pounds lighter at least?
More sport oriented wheels with disk brake are certain to be lighter still.
-Alan