As of 2015, a good location to purchase used golf balls in bulk is the Golf Ball King website. Pre-owned balls can be purchased by the dozen.
The Golf Ball King website carries many popular brands, including Titleist, Callaway, Dunlop, Nike, Bridgestone, Taylor Made and Wilson. Shipping charges are added to orders under $100.
Another good location for purchasing used golf balls in bulk is Golf Ball Monster. The site carries used range balls and refurbished balls. The company offers over 800 products and free shipping on most orders. The Golf Ball Monster also buys used golf balls. Visitors to the site can search for balls by brand, grade and model.