I buy a $10 book on Google Books, $3 goes to Google, $7 goes to the publisher. I buy the same on the Kindle Android app, $3 goes to Google, ?? goes to Amazon, < $7 goes to the publisher.

Since Amazon had been selling books on the Kindle app for a while, I assume they made more than 30% to be worth it, or pushed the cost to the publishers? Or probably worked out some deal with Google, which seems a bit unlikely.

Amazon's cut is 60%, 75% if you're not in an Amazon exclusivity deal (you also won't get boosted).

So basically Google 3$, Amazon 4$, publisher 3$.

If you go to Amazon marketplace directly, Amazon gets 6$, publisher gets 4$.

Amazon complaining about predatory marketplace is rich.

For a long while everybody ignored the Google's cut from the purchases. Google only started enforcing it a couple of years ago.

Ah that makes sense. I think the workaround was that you could pay without entering payment information, but Google didn't go into every app to enforce this at the time.