Ryan Avent’s 90-page Kindle single, The Gated City, is a bargain at $1.99. It was produced in close consultation with the Kindle Singles editor, David Blum — the gatekeeper who determines what gets chosen to be a Kindle Single, and what gets relegated to the long tail of Kindle Direct Publishing.

We’re running a great excerpt of Ryan’s book at Reuters — it’s headlined “How home prices helped kill the first tech boom”. Basically, soaring home prices in Silicon Valley discouraged entrepreneurship, encouraged the flight of qualified workers to other locales, and meant that during the dot-com boom, Silicon Valley actually created fewer companies, per capita, than the country as a whole. With any luck, reading it (or other excerpts, here) will encourage you to buy the whole thing.

Meanwhile, last week Gothamist published its own debut 72-page feature story, in the same format — a 72-page e-book. After putting out a call for pitches in July, Gothamist publisher Jake Dobkin decided that the first $5,000 commission would go to Patrick Kirkland — one of the jurors in the infamous New York “rape cop” trial. He’s not a professional writer, and the story is a bit clunky at first, but he becomes very fluent during the crucial central part of the book, where he explains exactly why and how the jury managed to unanimously acquit both police officers of rape. As someone who found the verdict quite shocking, I can say that he convinced me, too, that the jury made the right decision.

Interestingly, Amazon’s Blum rejected Kirkland’s story as a Kindle Single, calling it “an interesting piece”, but not “right for Singles”. What difference does the rejection make? Well, the Amazon business model is that Amazon takes 30% of the proceeds of e-books, while the author/publisher gets 70 percent. That’s the deal Avent got. But if you just upload your book to the Kindle store, as Gothamist did, then you only get 70 percent of the proceeds if you’re charging $2.99 or more. If you stick to the $1.99 price point, then Amazon takes 70 65 percent, and you’re left with just 30 35 percent.

This is a serious incentive to get past David Blum’s velvet rope — not only will he help you with promotion, cover design, and the like, but he can also give you a much greater share of the proceeds for books sold for less than $2.99.

So when Gothamist published the book, it was $1.99 on iBooks, and $1.99 for the direct PDF download — but $2.99 on Kindle. And then things went exactly according to plan. Apple featured the book on the front page of the iBooks store, and Amazon — as it’s allowed to do — unilaterally cut the price of the book by 33 percent, to match Apple’s pricing. But it’s still governed by the initial pricing plan, so Gothamist gets 70 percent, rather than 30 percent of the current $1.99 price. (So, buy it!)

We’re still in the very early days of micropayments for books, but my gut feeling is that people are increasingly willing to pay small sums for shorter pieces in the 5,000 to 30,000 word range — much as they’re increasingly willing to pay small sums for apps. And the pricing models are, of course, still very much in flux. But if Amazon’s willing to give their Kindle Single authors 70 percent of the proceeds even after helping them with design and marketing, they should also offer the same deal to publishers who do all that work themselves.

Felix Salmon is an Audit contributor. He's also the finance blogger for Reuters; this post can also be found at Reuters.com.