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.
When Data was in 19th century San Francisco on Earth, he requested a need for some supplies from his bellboy. The bellboy told Data he could get him anything he needed for wholesale, adding "I can get it for you less than wholesale if you don't ask me where it came from." (TNG: "Time's Arrow")
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")