I G Farben had a number of factories and industrial units built around Auschwitz - the Monowitz complex being one of the largest - bombed by the USAF operating from Italy in 1944. Himmler courted the directors of IG to set up there the coal , water and good rail network being used as pointers as to why they should and the promise of labour from Auschwitz being another. The SS got paid for providing both skilled and unskilled labour , as far as I am aware the worker got zlich. (I will try and look up the agreed rate paid to the SS). The camp was said to have generated something like £125 million by todays standards towards the German economy. In respect of the people "resettled" - their property ( homes ,contents, buisnesses and savings) were stolen by the State before they were "deported" , ( some Allied states had to pay the SS for their transport costs) , and what transportable valuables they had when they arrived at the camps down to the clothes of their backs were "recycled" (stolen) and sent back to Germany. As far as large corporations such as "I.G." went they did no more than the dictatorship had already established as "the norm" . "Selection" on the arrival ramp at Birkenau was just an extention of this - it started with "T4" which again was costed to produce a projected saving - projected into the 1950's as to monies saved on care and fodd which would not be expended on "the useless eaters". ( I will try and look up this figure ). The camps ran on the same premise - if you could not work you died , why is an exact figure for deaths at Birkenau not known - in part beacuse it was not worthwhile counting people who had no value - as long as they died nothing else mattered. Hard it may sound , but this is the value system which drove the state , it was the moral compass which saw people as a slave resource to be exploited for maxium profit. This is what hanged Saukel and really should have given the same fate to Speer. The nature of the state itself which permitted and depended on the use of slave labour - making it the norm in the occupied east underlines another aspect of what the camp system was really about , this did not start with the war - it had been an increasingly important economic aspect of how the State was being run even before the war. This may read rather blured in that the links between IG , the industrialists and the SS are seamless but this is what the system produced and basically how it ran. As a slave state it had few rivals other than Rome. The stone to rebuild Berlin as "Germania" was to be supplied by slave labour from German concentration camps who would also supply no doubt part of the labour ro build the wonderful new buildings which Hitler would glorify himself ,the party, as he put it "what counts is building for eternity".