In the past, I remember stevia being sold as pure extract, standardized to 80% stevosides. But, now Vitamin Shoppe and NBTY delutes it down to only 25% stevia, with the rest being some type of plant fiber, yet they charge the same price. As a result, you have to use a lot more of the powder to get the sweetness.
I think most supplement companies are just like prescription companies: only interested in profits, not consumer health. For example, if Wyeth offered enough money to buy off NBTY and Vitamin Shoppe in order to shut them down, I think they would sell it, if the price was right. This is why I am glad we have LEF. If we don't at least buy just one of our supplements from LEF, they can go out of business, esp. with all the companies going bankrupt at the moment.