Besides POWs and Sauckel, another source of foreign labor was the SS. Through the practice of “Selektion” it sifted those useful or not for work. Part of the concentration camp population to arms was rented out to arms producers. This was done on the basis of units of labor, not specific individuals: when a worker died or became unproductive, the SS provided a replacement. For employers, the profitability of camp labor compared to hiring Germans depended on the fees charged by the SS, the cost of hiring overheads for the new workers and the money won from the official procurement agency for the job. Ultimately the Reich was both selling labor to the producer and paying him for a task. In the construction sector, camp labor was profitable but less than hiring Germans; it was still used simply because sometimes it was the only labor available.
A notable example of this kind of labor was the IG Farben chemical plant in Auschwitz, larger than the camp west of it and part of a wider industrial complex in Upper Silesia.
In addition to providing workers of its own, the SS was also instrumental in managing foreign workers from other sources as it kept them in line and held unruly workers in its camps.

The German economy was unprepared to handle such a large influx of labor. There was much waste at first and it took a long learning process, until late in the war, to finally assimilate them into its metabolism.
Among Soviet POWs brought for work, the high mortality of this category of prisoner continued within Germany. Meanwhile, Sauckel’s Ostarbeiter arrived so fast adequate housing and food could not be provided. They, too, had a high rate of attrition at first. Even after initial complications, they were mistreated, overworked and given limited food rations; the December 1941 ration for Soviet POWs and Ostarbeiter had a nominally high daily calorie value of 2,500, but it was of low quality with little fat and protein, and the real ration received was often less than that. Administrators were negligent and rations leaked into the black market. The populace resented the new arrivals and frequently accused authorities of favoritism, such as the case of Italian POWs who received more fruit and vegetables in accordance with their diet. The presence of so many foreigners clashed with ideology.
Tens of thousands of weak laborers had to be sent back to the East in the autumn under haphazard conditions and many died on the trains. Poor conditions became known in recruitment areas and voluntary enlistment withered away. Escapes became common among this population. The Gestapo registered 42,714 between April and July 1942, with 34,457 recaptures.

Besides mortality, another problem was a productivity lower than that of Germans, particularly among POWs. Mortality and productivity were both tied to the treatment of workers, particularly the question of food. In sectors such as coal mining caloric input had a direct relation with productivity. Mere days after Sauckel’s appointment the Wehrmacht’s military-economic office wrote to him that a well-fed group can outproduce a poorly-fed group twice its size, and feeding workers only barely enough to keep them alive would be a net loss to the war economy.
The wastefulness of these questions was immediately realized. In early March the Mitteldeutsche Motorenwerke complained to the Food Ministry of insufficient rations, noting that unlike in the East, where replacements could immediately be provided, the loss of an Ostarbeiter working special machinery in Germany to malnutrition meant a lot of time wasted training his successor. Large-scale death and underperformance nullified much potential productive capacity.