Is this actually worth it - beyond the margin per sale?

Amazon does not compete for your reader's next purchase by accident. They compete for it deliberately, systematically, and with extraordinary sophistication - because they understand something that most publishers have not yet fully internalised:

The reader relationship is worth far more than any single sale.

When a reader buys your book on Amazon, Amazon captures everything: the purchase, the reading behaviour, the completion rate, the review, the browsing that follows. They use all of it to recommend a book from a different publisher the next time that reader opens the app.

A reader who buys once and returns is worth multiples of a reader who buys once and disappears into a retailer's ecosystem. A reader who subscribes is worth more still. A reader who joins a community, recommends your books, and becomes an advocate is worth more than any marketing budget.

The margin improvement is real: 150 direct sales a month at 85% margin versus 30% is meaningful. 100 readers at £5/month is a recurring revenue floor. But the real compounding is in the relationship - each direct reader is a reader you can reach again, for free, forever.

Amazon can out-algorithm any publisher. But no algorithm can replicate the relationship between a publisher and the readers who genuinely care about what they publish. Direct is how you build that relationship at scale.