What the specific differences is in the OEM branded fluids, I am not exactly sure. One says "gear oil", the other says "high performance gear oil". And many (most) of the aftermarket quality brands specify the same fluid for both applications.
The difference in price, especially given how little is needed for a change and how infrequently that change is needed, amounts to a very small dollar difference and really is not that big of a deal. If it is, you probably are driving the wrong kind of car. However, I do agree that the difference in price for the OEM branded fluid is a bit of a head scratcher.
Generally, unless something flat wasn't available in one of the trusted aftermarket brands (Pentosin, Liquimoly, Motul, etc.), I wouldn't go after the OEM branded stuff anyway, as Volkswagen tends to mark that stuff up a lot and they obviously source it from someone else. I've gotten OEM fluid before that was in a bottle that clearly had a Texaco logo on the cap.