I agree with derk -- Goldentime is pretty much like a German FKK.  It's accessible by U-Bahn with about a 15-minute walk, unless you have a rental car.  The facilities were large, spacious, and clean.  There used to be a second, smaller FKK across the river near a park with a big Ferris Wheel.  The name used to be Dona Dolls or something like that.  Prices are higher than a German FKK, but, not that much higher.

The $400+ figure you're citing comes from Babylon.  It's basically a night club/restaurant where you pick out a girl, have drinks or dinner with her, and end the night with a session in one of the rooms.  It was way out of my price range and a little too close to my hotel and my colleagues for comfort.  On another board dedicated to overseas hobbying, there are a bunch of Canadian guys who swear by the place.  

I vaguely remember that there were a bunch of smaller apartment-type brothels of varying quality that advertised in various papers and on line.  Regardless, even the limited scene in Vienna is hobbyist's paradise compared to anything here in the U.S.