The cheaper the vitamin, the cheaper the manufacturing standards. Walmart and other \"budget\" sellers need to still make money, therefore they usually use a lesser quality of raw materials. You do not need to get the most expensive out there and I would stay away from MLM companies unless you can get answers to the following; Are they manufactured in a GMP or pharmaceutical lab?
do they guarantee accurate labeling? purity? potency?
do they have chemical assays on file?
You have to remember that supplements are not regulated like other over the counter drugs and there has been a lot of problems within the vitamin industry.