It's kinda amazing how Unity shot themselves in the chest with this one. No, I don't mean foot, they are now actively bleeding from the torso.

No Dev or Publisher is going to be okay with this, none. This basically leaves Devs on the hook for unlimited liability. Even with their walk back of "only initial installs" doesn't help. I myself have both a Desktop and a SteamDeck. That's possibly two installs out of the gate from one customer. Then any time I make an upgrade in the future, or heck maybe even switch Proton versions on my Deck, the Dev could be on the hook for more cash. There's zero transparency with how these "installs" are detected or counted, so there is no way to budget or plan for the expenses.

Businesses hate unpredictable fees.

They'll deal with utilities upping rates, because who are you gonna switch to in a monopoly? But if you're just a tool for them, they'll ditch you as soon as they're able and never use you again.

And again, publishers will care about this too, since their whole job is distribution. Any Dev looking to sign with a publisher, even a subscription service like GamePass, will now be asked which engine they're using, and I bet you 9/10 times the Dev will get rejected if they're using Unity now. That puts even more pressure on Devs not to use Unity.

Unity will price gouge their existing customers(Devs), but will ensure that nobody ever buys their product ever again. At this point I doubt their reputation will ever recover even if they can walk this back. The fact that they believe they can unilaterally add enormous fees at the drop of a hat means they've ruined any trust their customers had in them.

Unity: I can charge you any fees I want, any time I want.