$6K is about what I remember as well for the Stuttgart top. Crap, I paid less than half that for the factory one installed!! I did have my share of problems, however!
http://986forum.com/forums/showthread.php?t=7407
Another top, this one is made in England, as I recall. Not too pleasing to the eyes.
http://986forum.com/forums/showthread.php?t=6564