Once a year, the merchant visited the town. She brought strange goods from far-off lands, exotic spices, and treasures beyond compare. She would sit in the town square with her wonderous stock arranged around her and wait for someone to come and make a deal.
When the townsfolk saw her coming, they closed their curtains and locked their doors. Everyone knew the cost of her mysterious and enticing wares.
But every year, she would strike a bargain. There would be a rebellious teenager or a traveler who dismissed the townfolks' warnings as superstition. The merchant always got what she wanted.
Black Friday
Nice; sounds like a somewhat less actively malevolent version of Needful Things.