From the man himself:
The engine is basically free. You pay 5% of your gross revenue, but only if it’s more than $3000 for a given quarter. So, if your game makes $3100 in Q1, you would owe Epic $5 for that quarter, and that’s all.
Pretty generous, and kinda of a big deal.
I think this carries certain implications about the overall relevance of virtually every other engine in existence, including the BGE.
What do you think?