It's 0,5 USD for every install after the first 1 000 000, per year. Updates don't make any difference. Worth noting is that a user who never opens the app after the first time will still count as an install.
There is a couple of interesting ramifications there.
1 obvious, so, they just disincentivised updates? Brilliant. Or maybe the idea is for app developers to charge for updates.
2 oh right, developers have to update frequently or else Apple will remove the app for being a security risk or simply no longer being compatible with current os and apis, os and apis whose changes are controlled by who again?
So they charge for updates, and make it a rule that you must update.
They count as downloads but the count is download/per-user/per-year. Still not going to be cheap but yeah. If you have 2M users and you ship 1 update or 1,000,000 new updates in a year you just pay $0.50/user (for 1M of them, since the first 1M is "free").
However on the flip side a user can be someone who downloads your app, pokes at for 10 minutes and deletes it. Not something I would call a user, but for apples purposes it works.
(It’s per year, not per month.)