I'm not sure if this was the case in Munich, I could be off on the details but if remember correctly the city built it for 2 clubs (Bayern and 1680) and the rented it to both clubs. Later when 1860 yielded because they couldn't pay , Bayern bought all the shares. Also both the Autobahn (Äusserer Ring) and Mittlerer Ring(North) were restructure at this time for other reasons(traffic)so cost cannot directly be added to the stadium. So yeah I think this staduim was supported by public money, but I think it really is hard to put a number behind this.