Ouch. I wrote a travelogue as a side project/on a bit of a lark, and I enrolled it in "KDP Select" (Kindle Unlimited). I make far more money, it seems, from full-price purchases than my per-page royalties from Kindle Unlimited. It really seems that it doesn't make sense for most authors, since the revenue-per-page is diluted by these scammers.

EDIT: To put some numbers on it, here's my KDP dashboard: http://imgur.com/lDWoQQ6 The book is $4.99, of which I receive 70% ($3.50). I sell about 3 copies per day (making about $10), and generally get ~350 pages read per day (making $1.50). So I make 10x on regular sales what I do on Kindle Unlimited. If it matters, it's a short book of ~300 Kindle-normalized pages.

While writing this up, I realized Amazon charges authors $0.15 per megabyte of book file size per download. My book was 10 MB thanks to a bunch of photos. After extreme JPEG compression I was able to get it down to ~2MB or so. I wonder how many authors, like me, are losing 20% of their royalty without realizing it.

On AWS, you're charged ~$0.09/GB of bandwidth out. How Amazon thinks 1000x pricing is fair here is beyond me.