Did contract manufacturing in the nutritional supplements business for about 6 years early in my career. These guys sell the same product over and over again, sometimes adding a new ingredient of some type that's recently become popular. From Ma Huang (the MLM glory days) to garcinia cambogia, you feel something when you take it so it must be good. Typically, for the big MLMs, the quality is decent, the formulas are sound (weight loss/energy supplements aren't that difficult) but they'll be massively over priced. You are paying $50/$60 for a bottle that took $3-$5 to make. These companies rely on "friend" networking so much because they know that their products are decent and the massive marketing pitch they've built around it will combine nicely with the trust you have in your friend/acquanitance and the image they are portraying to you about "the business"