This is of course not including the yearly Unity subscription, where Unity Pro costs $2,040 per seat (although they may have Enterprise pricing)
Absolutely ridiculous. Many Unity devs are saying they're switching engines on social media.
If I had to do something like that, I would make it every time the installer runs, every time it's installed by a launcher like Steam, and as a fallback every time the game executable runs for the first time unless an installer or launcher hands it a key to say "you've been paid for already." But I'm by no means a game dev so idk.