Flour mill, oil expeller, thresher and stone crusher owners who run machinery off an electric motor or diesel engine through a V-belt drive are the buyers, and they call you the moment a belt snaps or starts slipping and burning during a working shift. Every hour their mill sits idle is lost income, so they are not price shopping, they want the correct matching belt in stock right now.
Mechanics and equipment fitters who service these mills are a second buyer, since they carry a customer's broken belt or worn pulley in to be matched rather than guessing at a size. Today many of these buyers get whatever belt a general hardware shop happens to stock, which often runs loose, slips and burns out early. The moment to pay is a stopped machine, so being the counter that always has the right size is the whole business.