Unless we're the owner of the website we can't know for sure exactly how much those big websites earn. But I estimate that the big blogs earn around $3,000.00 per day or more and the bigger websites such as yahoo answers, yahoo, reddit and quora earn probably $6,000.00 per day or more.
But they have employees as well that they have to pay so it's not all profit for them.
Most likely the earn more than my estimate but I can't know 100%.