Let’s say the average is 75. Lets deduct another 25 because it’s probably the same guy.
At 200$ per link (low end) thats 10k per month.
50 blog posts with each one linking to a gambling site is kind of unrealistic though. But the numbers (and the demand) is there. I am sure the actual market is in the hundreds of millions for this kind of a scheme.
And even though it is easy money, I think Google probably has a good grasp on identifying that a mommy blog is linking out to a gambling network.