The metaphor is backward actually. The Nazis transitioned to gassing and extermination camps because the leadership saw first hand the psychological problems of

The metaphor is backward actually. The Nazis transitioned to gassing and extermination camps because the leadership saw first hand the psychological problems of having ordinary people commit mass murder, not because it was cheap. It was probably far more expensive. Think of all the war time train and supply usage. > During a visit to Minsk in August 1941, Himmler witnessed an Einsatzgruppen mass execution first-hand and concluded that shooting Jews was too stressful for his men. By November he made arrangements for any SS men suffering ill health from having participated in executions to be provided with rest and mental health care. He also decided a transition should be made to gassing the victims, especially the women and children, and ordered the recruitment of expendable native auxiliaries who could assist with the murders. Gas vans, which had been used previously to kill mental patients, began to see service by all four main Einsatzgruppen from 1942. However, the gas vans were not popular with the Einsatzkommandos, because removing the dead bodies from the van and burying them was a horrible ordeal. Prisoners or auxiliaries were often assigned to do this task so as to spare the SS men the trauma. https://en.wikipedia.org/wiki/Einsatzgruppen#Transition_to_gassing https://en.wikipedia.org/wiki/Einsatzgruppen#Transition_to_g...