Ever wondered why Germany, an established industrialized country much like the USA still have an export economy similar to AsiaPac countries like Korea?  It cannot be artificial wages, nor currency manipulation to the extremes of AsiaPac countries (EU does manipulate it's currency on the free market, but does not tie it to the US dollar).

Well, what can it be then?

Quite simple as this comparison shows:

USA auto import tariffs are 2.5%, while Germany's is 29%.

Hows that for free trading, and some think Trump is crazy for threatening a 35% tariff.

Fact-checking though, Germany's listed official tariff is 10%, but they impose an import VAT on top of that of 19%.  We hear constantly from the Bush administrations, and Obama's as well, that USA enjoys a 3% tariff rate for imports into the EU.  The trouble is in the fine print which is that's just the average tariff rate of all goods.  The ones that contribute to the economy greatly have much higher tariffs.  Those administrations don't count the import VAT tax as a tariff, but it is the same.

I think you nailed the real reason without discussing it.

The Germans have made a concerted effort over the last 60 years to protect their industrial proletariat from exploitation by the rapacious owner class. Hopefully our newly elected comrades here will begin to do the same. Democracy is truly the road to socialism. Onward!

Haven't they been using the EU as essentially their own closed market?

Umm, Germans pay that same 19% VAT on German autos when they buy them as their domestic cars, and their .gov also requires domestic purchase of Opel, BMW, VW, Audi, and Mercedes just like ours requires purchase from the Big Three.

the 19% is paid for everything Germans buy - TV's, Microwaves and so on

the only item that has a lower Tax is food.

but unlike here the VAT is already part of the price - here it is being added onto the purchase.

Another factor is a highly educated and trained workforce, Germans still value trade schools and apprenticeships.

They also have excellent infrastructure and they're in the center of Europe, which means that most of their trading partners are right next door. If the US wants to export goods to someone other than Canada and Mexico they need to haul them across the sea.

Bought a HD soft tail for my German cousin, through the overseas purchase program when I was stationed there. I held in storage for a year (required) and then he registered it. I think I paid about $12k for it and when he registered it he ended up paying another $10-12k in custom taxes.

The other thing to understand is Germany has customerwise built up their auto industry. So many people want Mercedes, BMW's and Porsche's that they are a premium vehicle in the customer's eyes. While the American cars are quite looked down on, due to poor quality, poor design. The German cars aren't any better quality wise but most are designed around decent performance, so the customers world wide buy into them German dream.

Having been involved in the automotive field at the dealership level for decades I say OP your missing a major point if not the whole point.
I've worked on or at jap, german, domestic dealerships I can tell you it has more to do with design and functionality.
People will pay a premium no matter what the premium for the perception of the best no matter what the product.
German design and builds are different, they put a emphasis on the connection to the driving experience. That connection sells because of a multitude of reasons that have nothing at all to do with price.

From my point of view it has more to do with auto and manufacturing culture than market manipulation.
I not saying market/economic manipulation isn't going on, I'm saying it's not the reason German cars sell well world wide.