Wholesale was the practice of selling goods or merchandise to retailers or professional users. Wholesalers were typically close to producers of goods, as opposed to retailers who were closer to customers. This allowed wholesalers to sell goods at a reduced cost.
Grand Nagus Zek, in 2371 told Emi where she could get self-sealing stem bolts at wholesale prices. He did this much to the dismay of Quark, as Quark was about to broker a deal to sell Emi the bolts she needed himself, at a much higher retail price. (DS9: "Prophet Motive")