how many pints cooked cabbage from 3 pounds raw?
It really depends on how much you cook the cabbage.

Less cooking not only means that it's firmer and it won't compact as easily, but that the majority of the water is still in the cabbage, adding volume.

The longer that you cook the cabbage, the more that the cell walls break down, moisture is expelled, and that moisture evaporates.  (but evaporation is also a function of the surface area of the pan/pot it's being cooked in)

...

I've personally never paid attention to the volume of cooked cabbage, but I have for cabbage that's been salted, let sit and drained to make cole slaw ... and that's closer to 1.5 to 2 pints per 3 lb cabbage.  (but again, it depends how much force you use to pack it ... and how much you cut out when removing the core).

I'll try to remember to get a measurement when I make a ~10lb batch of cole slaw for a gathering in two weeks.