It's not "mass hysteria" to observe that your business partner is willing to attempt to retroactively change the terms of your arrangement with them, and therefore decide they aren't trustworthy as a business partner. The actual monetary cost to developers is actually quite inconsequential compared to the lack of integrity Unity showed in trying to make this apply to games which were already released.
When they tell you that you have to report your installs and sales each month just like you do your taxes, that's when you notice there are other free engines.
At least one publisher jokingly (but not jokingly) said "developers: make sure you include which engine you're using next time you pitch us a game!"...