*The Tattooist of Auschwitz.
(media.scored.co)
OK, 6 million tattoos across 5 years adds up to about 1370 hours of daily tattooing labor, so you'd need a crew about 100 nazi tattooists working 14 hour days 7 days a week for years on end. Certainly this would have been a great expense for The Reich and it would have been mentioned in budgets somewhere in the paperwork, do any such records exist? What about the cost of equipment and ink?