Well, let's just see if that's true. EVERYONE, click one of my ads every day and I'll make a graph. (JOKE)
It depends, did your friend click of the ad from the same computer? If so then it will be the same IP and google will pay less for that, if at all! Also, the payment depends on your CTR so when your CTR is bigger then you get paid more, its a way for google to reward you