Offshoring and Sweatshops, 1940s Style
Auschwitz was not just a way to get rid of Jews, it was also a major source of cheap labor. As Richard Rubenstein points out in The Cunning of History, "I.G. Farben's decision to locate at Auschwitz was based upon the very same criteria by which contemporary multinational corporations relocate their plants in utter indifference to the social consequences of such moves." I.G. Farben invested over a billion dollars in today's money at Auschwitz and, thanks to the endless supply of labor, adopted a policy of deliberately working the Jewish slaves to death.
So I guess you could say that working for I.G. Farben was the "best available alternative." All I can say is that it would be better for those who determine the range of "available alternatives," then and now, if they had millstones hung around their necks and were cast into the sea.