Puritan's Pride offers two Navitas Naturals Organic Mulberry Berries 8-oz. Bags for $19.99. (Add one bag to your cart; the extra one adds automatically.) In-cart, it drops to $19. With $4.95 for shipping, that's the lowest total price we could find for two bags by $7, outside the mention below.
Of note, with orders of $25 or more, Amazon charges $15.94 with free shipping for Prime members. (Note that this item is part of Amazon's "Add-on program" and can only be purchased with an order of $25 or more.)