"Please slay these monsters!" we told the hero, "And bring back twenty of their fangs as proof that you accomplished this deed."
The hero looked offended. "You're begging for my help, and then requiring proof because you're worried that I might somehow FAKE saving your village? You're awfully ungrateful. How about I just save your village from these monsters and be on my way?"
We replied: "Oh, you can slay all the monsters you want, but if you bring back twenty fangs, we'll consider you to have finished this quest. Then you'll get a five percent discount on the overpriced goods and healing items that we sell."
The hero looked skeptical. "Are you sure your village is really in danger? This sounds more like a coupon-collecting ad campaign than a genuine plea for help."
We replied: "Well, we need proof, you see. I mean, sure, you're a legendary hero who's probably got better things to do. But you won't have our gratitude unless you bring back at least twenty fangs."
The hero shook her head in resignation and left without saying another word. She didn't even search our homes for valuable goods.
I assume that means we're saved! Yay!