If you’re at the point where you’d have to share your profits with unity, your game will be making enough sales that it’s probably big enough for unity to notice it. And if you manage to keep your copyright infringement hidden from them, then your game is probably so small that you wouldn’t be paying anyways.

From my experience that is not true. Unity has a very dedicated team of lawyers who are constantly looking out for possible licence infringiments. And they would rather inquire twice than to ignore someone for being “too small to notice”.

How I made this experience: In univeristy I worked on a research project regarding immersion in gaming. We used Unity for creating virtual environments to conduct our experiments. For that we acquired a couple of education licenses which were strictly bound to non-profit usage. In return we got them for free. Some months later we received mail from Unitiy lawyers who suspected that we broke the terms of our license. The matter was cleared up after a while. But still, I was astonished by the dedication and energy they invested. It makes sense though. Their business depends on it.