IME it depends on what/which supplements you're talking about. We have a mental list of brands and vendors we'll use for different things, and then shop price among those brands/vendors when we need to order something. It's worked well for us—we can usually save ~25-30% over a year. We do make use of Puritan's yearly sales (like now—buy 2/get 3 free—ends Tues) when it makes sense to. Their stuff is generally high/overpriced, so we still go through the whole shopping exercise.

Supplements are one of the businesses/markets where the consumer can actually make out fairly well because there are so many competitors vying for the same business.

Doc