Valve co-founder and managing director talks piracy, sales and economics:
One thing that we have learned is that piracy is not a pricing issue. It’s a service issue. The easiest way to stop piracy is not by putting antipiracy technology to work. It’s by giving those people a service that’s better than what they’re receiving from the pirates.
[...]
We do a 75 percent price reduction, our Counter-Strike experience tells us that our gross revenue would remain constant. Instead what we saw was our gross revenue increased by a factor of 40. Not 40 percent, but a factor of 40.
Full transcript (it's not very long)