The Nazis killed something like 14,000 people per day once the Holocaust was in full swing. That’s gas chambers, then moving bodies to the ovens, then emptying out the ovens, and then repeating the cycle. And they found this was the most efficient way to kill large groups of people. If they could have killed more people faster for cheaper, they would have.

Crushing 10,000 people and hosing them down a sewer would probably be the most sophisticated sewage system ever developed. Hell, even crushing 10,000 people with tanks is unbelievable.