"The killer is explaining where the money comes from without losing them trying to explain the economic model and the inflation and the reward pool distribution and...and...and..."
It really helps if the person in question has a solid understanding of economics. Of course, I realize that's a rather shockingly small demographic these days.
If they understand how the money supply is currently created in the West from nothing (communal inflation), then the idea of Steem should immediately seem plausible.