Commercial soylent is overpriced. However, you can DIY for <$5/day, even if you need unusual amounts of food. Compare that to these numbers, which were the first thing I found. My $35/week is about 19% less than thriftiest food budget using conventional food for my gender/age. Plus I'm fairly large (but lean), active, and trying to add muscle/not lose weight, all of which should increase how much food I need relative to average.