Lostgolfballs.com. Amazing deals on Prov1's. Get their AAAA grade which are almost like new. Can get 50 for under $50. Much better than a new dozen for $45.I buy used pro v's. Saw a small driving range in Jeff, Ind on fathers day and picked up two dozen used pro v 1 for $16 on a fathers day deal.
Also play DT solo as well as I get two dozen used on Ebay for $13 with free shipping.
Never buy new balls.