The total costs for a game aren't just the development budget - there's advertisment, logistics, shelf space, and of course final Q&A. These usually add up to about as much as the development costs.
So, it can make sense to cancel a completed game as well, if it's sales predictions are that grim. Yes it might have cost 10 million dollars, but is it better to lose this money, or invest another 10 million and lose 15 million in the end because of absymal sales?
Which is why it has happened many times before... AFAIK the Babylon 5 game was one that ended up like this, despite online petition campaigns and all.