Like with most things buying in bulk is where the savings are. For pins it sorta depends your volume and/or storage space. For lower volume sign up for cleaner's supply's mailing list and watch the sales. Every little while they have sales on safety pins which put them cheaper than race results at that volume, and they'll ship free over a certain amount (much to my delivery driver's annoyance lol).
Larger volume prices tend to really drop at qty of 100 000 or more (~4$/1000), but warning 100 000 are both heavy and take up a lot of shelf space if you're not doing that sort of turnover lol.