Does anyone have any recommendations on FKK clubs in Vienna?  Also, how much do they cost?  If I was interpreting one website correctly, the total cost (room + lady) could be ~400+.

You're pretty much stuck with "Golden Time" not associated with the one in Germany. Slightly higher prices but the same basic idea. Babylon is another club in Austria with a few locations but upscale, perhaps more then you'd want to spend. Your best best is to check the local paper and search the internet. See the link before and check the other info at that site.

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.