Close to nothing, honestly. If the only reason the users are signing up is to win a free iPad (especially with the odds being only 1 in 1,000) I severely doubt

Close to nothing, honestly. If the only reason the users are signing up is to win a free iPad (especially with the odds being only 1 in 1,000) I severely doubt that any of them would convert to paid customers. Now, if you could send 1,000 paid customers my way in that time, I'd be extremely happy to offer you 65% of the initial revenue generated.