Ugh... paying a percentage off the earning after reaching the limmit or any at all is what makes me uninterested in buying a product in the first place. It is only extra complication for the creators of the program to get the money. The license you seem to point out like the unreal pack is more for companies than proffesionals.
But you could question yourself, do you make this program for game creators, or just to get money out from everywhere posible? Its not easy for me to explain...
You see, I for example am a freelance animator and not only purchased but also crossgraded to toonboom animate PRO2 mainly, because aside of tools that i need, its license after purchasing it once, allows me to use the program for anything i want without any further dealing.
And that is what i preffer on a product that i pay for.