yes your website's content and keywords determine which subject of ads appear... certina subjects pay more than others...
i only slightly have that problem. maybe 1 or 2 2cent or less clicks. so far this morning, 4 clicks = >$2.00. i think what most people's problems with cheap clicks, is because they're shooting for the high paying ads (mesolo-whatever, student loans, etc). and there are so many MFA sites out there for these topics buying adwords, that you are creating a viscious circle of driving down your own revenues.