For many years, packaged vegan foods were expensive, sometimes unappealing, knock-offs of animal products and byproducts made for diet extremists. Not any more. Companies that make plant-based fare, such as Treeline Cheese and Beyond Meat, want their products to go mainstream. They're working hard to appeal to meat-eaters, not just vegetarians. Others, like Santa Margherita Wine, call being vegan more of a perk than a goal. But will Americans ever really be willing to spring for a more expensive cashew-based cheese or skip beef for an imitation burger?