Until now, most people probably only considered consuming marshmallows while sitting around a bonfire and roasting s'mores. But now, marshmallows are making a comeback--and getting a luxury makeover, too. Yesterday's mundane Jet-Puffed marshmallows are being replaced by gourmet concoctions with caramel swirls and even passion fruit. Why now? "What's trendy in foods these days are nostalgic, classic foods," said Suzanne Lombardi of Whole Foods. Thanks to the new wave of marshmallows, the industry has increased sales by 7.4 percent through July compared with the same period last year. But the treats don't come cheap: A one-pound sampler of gourmet marshmallows goes for $28 at Dean & DeLuca, while a sack of 16 caramel swirl marshmallows is priced at $5.99 at Plush Puffs Gourmet Marshmallows.