No idea about production numbers, but I can give some feedback on the game...
IMO, a big reason it doesn't get much love here is the voice calls. Stern went with voice actors on this game, and they SUCK. Their "Batman" sounds nothing like Bale, and their "Alfred" can't even pull off an English accent.
It's not a bad game, but in my view it's basically a one-trick pony (the crane). Now, mind you, it's one hell of a trick, but one trick none-the-less. Also, since it's the biggest feature on the game, and really part of that final sequence of the second movie, why isn't the crane tied to the Joker? Why Scarecrow? Heath Ledger's Joker was one of THE most iconic movie villains of the past 5 years, and on this machine, he's almost an after-thought.
All in all, BDK has some good ideas, but the integration/execution falls flat.
YMMV, of course.