[N]ot only do contributors self-publish, but they are paid according to the size of the audience they attract … [E]ach contributor gets paid a certain number of cents for every visitor per month.
There is a clear incentive for them to get repeat custom, as they get paid 20 times that amount if the same person reads another of their posts during that month.
According to the piece, last year “two contributors made more than $100,000, several made $75,000 and 25 made $35,000”. And, one assumes, 900+ made not very much at all.
You can read the full piece here.