Question

what was hollow cost

Answer 1

It's Holocaust.

Mass genocide of Jewish(and other "inferior" in their view) peoples by the Nazis.

Removing of Jews(jewish).

Answer 2

The Holocaust, also referred to as the Shoah, was a genocide during World War II in which Nazi Germany, aided by its collaborators, systematically murdered some six million European Jews, around two-thirds of the Jewish population of Europe, between 1941 and 1945.