Liquid diets are not exactly a new idea, and most of them don't have to be prepared at all but come in portions. Since most of them have been developed for medical use, the price tag is significantly higher. Some of them have been developed for patients who can't swallow normal food at all, so I doubt they lack anything important that Soylent contains and probably have been much more rigorously tested. If anyone knows studies that have been done on these people, I'm all ears.