I have both an OEM a-duct, and an Abflug replica. Of all the replicas I've seen, the Abflug is the best.
OEM (mine is brand new, never used, only opened for pics)- I paid around $550-$600 for, possibly a bit more.
The Abflug I paid $200-$250 for. (before I came across the real McCoy;))...