One Click for Big Dollar

I am surprise when I checked adsense report last day. I got $5.22 for one click. This is amazing for me because it don't happen to me before. I know this can be happened for every adsense publisher. Even maybe they can get higher commission for one click.I don't optimize content for earning huge commission on every single click like that. I also don't have secret how to do that. There is no key or secret about this. It just comes from what we call high paying keyword. And maybe my site topic is also high paying keyword too.