It seems that editors get paid per successful Boost. So if you sign up to become a Booster (anyone editing a publication can do so), you can potentially be selected (it isn't just being trialed anymore, anyone can apply). I've been Boosted 3 times in two months, so it doesn't seem that rare. One of my Boosted posts had made over $300 (the other two aren't nearly as good, alas). I don't know if the editor gets a percentage or just a referral fee of some kind, but writers of medium (meaning not large/huge) publications are definitely involved in Boosting already, AND getting paid, from what I've heard!