This might actually lead to that, depending on what kind of lawsuits arise from this change. Which could mean there will be pressure from others who don't have a stake in the "unity install fee" game but do have one in the "wants to change terms at a whim" game.
Or maybe it will threaten the "by continuing to use this, you agree" clause instead and open up a path to continue using a previous license agreement if you don't like a new one.
If that's the case then they could simply up the charge next year to $10 to get even more money for doing absolutely nothing. And then to $20 the next year and so forth. There's no sane court anywhere in the world who would say "Yeah, that sounds reasonable!" and even the less sane ones would think that's bonkers.
It used to be illegal. Part of anti-trust was forcing IP owners to license their technology to everyone at a reasonable price. That means that reddit’s API price gouging would also have been illegal and tesla and apple would have had to license their FSD and OS to other hardware manufacturers. This ability to control other companies through abusive pricing and licensing lock-in is classic monopoly violation that the govt has stopped policing.