Why would Epic base their percentage off of profitability or GMROI$? That would be ludicrous. Epic has no direct impact on profitability - why should they take a cut for bad marking / bad financial decisions / etc?
Let me try to put this into context - Imagine you have a cookie recipe that a bakery wants to license to make and sell cookies. You base your cut off of the revenue of cookies that are sold as the recipe is not a product / tangible good. Unfortunately the bakery burns the cookies / puts them in unattractive packaging / lets them sit in the warehouse too long and they go bad / the CEO gives everyone Ferrari's and trips to space / etc and the bakery doesn't make any money or looses money due to this. Is the recipe that you licensed to the bakery responsible for any of those decisions? NO! Your recipe has nothing to do with the bad decisions that the bakery made leading to their financial hardship.