Most people do not know that some anti-aging products come in different strengths.  For example, you can purchase Prevage at the store for $150 OR you can buy Prevage MD (which is double the strength) for $120 at your dermatologist's office or for less on ebay.  Why pay more for a product that is only half the strength?

Another example is N.V. Perricone's alpha lipoic eye cream, which comes in regular and high potency.  Often on ebay you can buy either one for around the same price.  I don't know about you, but I pick the more potent products.

By the way, both of these products are great!