@kagoda was asking for a meal replacement not for weight loss shakes. (Also, almost 5CHF per meal is not quite cheap, especially if it is only 200kcal.)
About the question:
It’s just food, not magic. Soylent tries to cover your macro- and micro-nutrient needs as well a nutritional science understands it.
Most people in the world survive on really simplistic diets (rice and beans, potatoes and corn, wheat and milk, etc. and then some proteins and fresh veggies added).
If you replace 7 meals a week with Soylent, and eat some other fresh food for the other meals, I struggle to see what the big problem is.
Try it out. Maybe you’re allergic to it. Maybe you can’t stomach it. Maybe you’ll get sick of it very quickly. But you won’t starve or die of nutritional deficiencies if you apply common sense.