Earlier quoted context omitted.
Lifetime royalty fee on any related worldwide gross revenue is a happy problem?
To be able to use this tech in the first place? I have no glue about business problems but this sounds far better then the 30% rip off by apple and Google app stores....
Sounds like a happy problem to me;)
By the way you don't only have to file a report for Epic whenever you release a game using UE, you also have to report them your yearly sales and calculate what income is "directly attributable to UE" for that game. For an ordinary small person, for whom you imply lifetime 5% off gross worldwide revenue is a "happy problem", this is way more involved (and prone to legal liability) compared to app stores. You will probably have to hire people well before the million mark to make sure numbers are OK and you don't accidentally owe Epic $$$$$.
I know which model I would choose. Probably the one where I raise prices by 30% and don't have to deal with anything else.