It depends on which beers. There is a great variety. Doppelbock commonly has about 8% to 10% ABV; sometimes even higher. On the other hand, there are plenty of American craft beers in that range. Oktoberfest seasonal "Marzen" beer in Germany is typically around 6%. Kolsch, Helles, and Schwarzbier are around 5%.
It's interesting how well-known Oktoberfest is so far away in America. When I was talking to some friends from Switzerland, they were unfamiliar with it.
We have an annual party in Erlangen, too. It is called Bergkirchweih. Everyone wears Dirndl and Leather pants. I don't go there because there are too many drunk people. This year was quite bad. I've never seen so many drunk people around when I was in town later in the evening. At least I would never go there alone as a girl or woman. Some girls report sexual assaults. As to alcoholic beverages: it is like Mallorca, Ballermann, and not really my cup of tea......