Let's not forget that many of these large retailers have moved to the practice of taking up to 90 days to pay their suppliers. 90 DAYS! That's three months before you see the money of the product you sold through their channels. And they do this because they simply can.
I believe that there's not a single retailer that doesn't leverage its distribution advantage to squeeze their suppliers. If you're not Coca Cola, PepsiCo, Unilever, Procter and Gamble or Colgate Palmolive, you have little to no room for negotiation.