I do custom application and have a dealers license and have found that they mean absolutely nothing to the wholesalers.  All the retailer/applicators are in bed with them so the wholesalers protect them from new competition.  Add to that most wholesalers hate farmer applicators.  Heaven forbid someone who sprays their own ground gets a better price.

My experience has been that only cash and volume talks and it talks the loudest during the late winter/early spring.   Shop hard and have cash or financing in place in December/Jan/Feb.  Many times one can negotiate darn near wholesale price, but it has to be cash and carry and at a time when their sales are down.  When a seller realizes cash is ready to walk out the door to save 1 or 2%, they somehow magically often will cut a deal.

If one is willing to put the time into shopping hard (especially online) you can get things cheap enough to sell them for the same price as the local retailer and make some money.  Don't expect a 20% margin, but  there is room for some margin.