http://forum.axishistory.com/viewtopic. ... 8#p1793968
I think that illustrates the point that I have been making. In 1944, Himmler wanted to use as many of the remaining Jews as possible for slave labour, rather than to kill as many of them as possible.And keep in mind that in 1944 the Nazis valued slave labor much more than in 1942. In contrast to 1942, the WVHA had much more of a stake in deported Jews in 1944. There had been frequent talk about converting Lodz into a full fledged concentration camp. The reason the death rate at Birkenau was so much higher for the Lodz Jews than the Hungarian Jews was that the Lodz Jews had been starving in that ghetto for over 4 years by that point -- the Hungarian Jews had lived more or less normally until early 1944. So there were only around 2000 Lodz Jews who were selected for labor (I should add that my grandmother and three of her sisters were amazingly among them; my other grandmother had been in a transport from Hungary just 2 or 3 months earlier and survived).
As you wrote, the reason why almost all of the deportees from the Lodz Ghetto were killed upon arrival at Birkenau was that they were in very poor physical condition, having been subject to malnutrition for four years. Presumably if they had been in better physical condition, more of them would have been selected for labour, to satisfy Himmler's increasing demand for slave labourers.
Thus, the reason why such a high proportion of the deportees from the Lodz Ghetto was killed was presumably not because Himmler was giving priority to extermination over exploitation for labour, but rather that most of the deportees were far to weak to be used for that purpose.