I'd tell ya but tax man might be listening.... lol....j/k, I pay my taxes
but on a serious note: some make money yes, and many don't, and then the ones that do will all be different from each other. Really depends on factors like, how are they setup to make money, how are they marketing themselves, do they get a good sponsor ratio of sales from clicks, is the webmaster business minded, does he/she manage their money right...lots of variables
Basically you can make as much money as you put effort in with a mix of creativity, smarts, and management.