I often see this brand of vitamin go on sale bogo at all sorts of places: drugstores, grocery stores, etc. If you go HERE and register, you can enter codes from the bottles. For each one you enter, you get 50 or 100 points. As you collect points, you collect "rewards" in the form of ... COUPONS! When you collect 500 points, you can print a $5/1 coupon!! The limit is 6, so keep hitting your back button.
With a bogo sale, and a $2.99/bottle (or in that neighborhood), and two $5/1 coupons, you've got yourself a moneymaker!
I know for a fact I've seen these bogo at Walgreens, CVS, Kroger and Rite Aid.