if it's a vit/supplement I found the best prices by going to Amazon and then looking at the links on the bottom of the page of what I was looking for (if that makes scene!)
Also, once you find a site, sign up for their e-mail list. Often you get a coupon in your into letter! Can help!
I did find this talking about different kinds of maca. I'd be very careful to buy this organic and from a major seller since it is so new and untested...