Can this really be considered lost revenue? It's unlikely that all 1,000's of the "free" games were going to be purchased at the current price. You run in to the same questions with piracy. Were the pirates really going to pay if they couldn't pirate?

The lost revenue should really only come from customers who would have paid the asking price but managed to get an illegitimate deal, plus whatever support and overhead costs can be applied to the game downloads.