But that was not what he was saying. His argument was that just because NY has such a high GDP does not mean they need to spend that much on their police force. The number of police (+soldiers) you need is more a function of the number of citizens and area.

Just taking your numbers above. The NY police has 50,000 police for ~8.5 M people. Germany has ~280k police for 80 M people, and that number likely includes border police, customs police, federal police (all jobs the NY police does not do). So NY has probably around 2x as many (regular) police per citizen as Germany.