So, they're making a third Riddick film - the first being Pitch Black, in case you were unaware. This may come as a surprise because the second; Chronicles of Riddick, cost "05 million and only made just shy of $60 million at the US box office.
So, why on earth is another being made? How can it be made? Quite simply, it's not the movie making the money, but revenue streams outside the box office...
What are we talking about here? Well, merchandise, DVD sales, broadcast fees and much more. But they often don't make enough money quick enough. In this case, we're talking about video games. Riddick's appearances on consoles appears to be generating enough acclaim and generating enough sales to warrant a revisit.
Ultimately, interest in Riddick has delivered the opportunity to produce another movie, even if it's another loss maker, because in turn it will generate interest to keep making more money via the games industry. Beautiful, isn't it?
Games Keep Riddick Movie Series Hanging Around [Wired]
Chronicles did perform shitfully at the theatre but has since made money from games and DVD sales (as you pointed out) as more and more people realised it was FUCKING RAD! Myself included.
I watched Chronicles of Riddick quite by accident (having never seen Pitch Black, and expecting any movie with Vin Diesel in it to suck balls) and was BLOWN AWAY by HOW FUCKING AWESOME and COMPLETE the universe was. It has since become one of my favourite movies and I'm one of these people who has sponged up anything to do with the franchise, including Escape from Butcher Bay and Assault on Dark Athena as a consequence.
Hearing that a third movie has the go ahead makes me feel warm and fuzzy in my special place. And in case you were wondering, my special place is THE PART RIGHT BETWEEN WHERE MY BALLSACK ENDS AND MY ARSEHOLE STARTS. You know - the spot your Mum loves.