In total, speed traps in Germany are estimated to bring in billions of euros in revenue (https://www.welt.de/motor/article13877289/Das-Milliardengesc...). There are many agencies which can place speed traps and profit - federal, country, county and city cops, in addition to city personnel and sometimes even private companies.
They are not a good funding source, but a very consistent one once you find the right spots to milk people.
http://www.who.int/violence_injury_prevention/publications/r... https://www.science.org.au/curious/technology-future/physics...
What you didn't mention is that (since removed) 15 M€ speeding trap was located on a downhill stretch with a high risk of traffic jams and not only placed for revenue.
German speeding fines are minuscule in international comparison. Just try "casually speeding" 20 km/h in any neighboring country.
Speeding is a German national sport leading to a vicious circle of decreasing limits even further.
No, it's two entities at the least in urban areas: the police and the municipality.
> German speeding fines are minuscule in international comparison.
Yes, which makes people speed in higher amounts and only because of this the system of traps bringing in 15M+€ actually works - yes you get the occasional dumb moron with 50+ km/h, but the most part is netted by the small fish speeding 10-20 km/h.