A) They're not in the business, and clearly have no desire to be in the business, of selling cases; they're in the business of selling horns;
B) clearly, they have run the calculations and come to the conclusion that the minuscule profit to be made from selling cases isn't worth the explicit, implicit, and non-monetary opportunity costs of doing so;
C) At $600 each, they clearly DO make a profit on the few cases they do sell to the suckers who are willing to pay it.