Approved pricing lists can work if you implement extreme social ostracism on breeders who sell under that amount. However everyone has an incentive to do backroom deals at lower prices to get stuff sold. This is actually quite a good thing for consumers because their goods are constantly decreasing in cost and the quality of the breeders must continue to increase if said breeders want to sell and stand out from the rest. Also, we should all be in a race to innovate and outcompete the masses. This is the only way that your business has a shot at surviving long term.