Yes but what we're looking at here is: can we use cognitive bias to increase the number of people who pay for the full version. So you give someone a demo for

Yes but what we're looking at here is: can we use cognitive bias to increase the number of people who pay for the full version. So you give someone a demo for free. They know it's a demo and they know it's free. They will be cautious about buying a full version. But if you give them a game for free, and then they find out whilst using it that it's only a demo, they will experience "loss aversion" and are more likely to upgrade since people experiencing loss aversion are more likely to gamble as they try to reconcile their loss.