Originally Posted by lomey
i agree, but my question is how to know our earning potential through statistics, like some categories have high cpc, so how to detect them?
The best way to find out which niches have high CPC's is by using the Google keyword planner. If you enter in the keywords or niches you want to target you can see what advertisers are paying to bid on these keyword terms.
For instance almost anything in the health insurance niche has CPC's over $20 per click. So if you found a specialized area in healthcare that you can target this could be a way to generate revenues. But keep in mind that usually high CPC's mean the niche you want to enter is very competitive even if you try to rank your sites organically.
I hope this answered your question.