Santorini Grill is a charmingly un-slick Williamsburg spot—lots of pastel colors and things made out of straw. It’s not the kind of place that you’re going to travel to—or at least it wasn’t before proprietor-hostess-cook-publicist Paula Douralas decided in November that she would let customers determine what to pay for their meals. The plan was to run the promotion for a month, but it’s worked so well and attracted so few freeloaders that she’s decided to make it permanent. About 95 percent of customers, she says, have been “very fair”: one woman left $80 on a tab that would have previously cost her $30; only a single person has left nothing—“A tourist. With a map in his hands. He liked the food—he ate everything. Maybe he thought it was a joke.” This reporter can confirm: It is no joke. In Brooklyn these days, there really is such a thing as a free lunch—but only if you want to be a total asshat about it.