IF YOU’RE THE type of modern citizen with a gym membership and/or a road bike, you’ve probably heard at least a little about cold-press juicing. Celebrities deliver breathless testimonials about their juice’s improved nutritional profile, magically legitimizing $12-a-bottle prices. And startups are popping up to capitalize on the trend—one raising $120 million by promising to deliver pre-packaged fruit, ready to be juiced on its proprietary machine. The science, at first, sounds pretty good. Good enough, at least, to convince consumers to pay up to $2,500 for the privilege of making the right kind of juice at home with…