I don't know anything about the Flower Garden pins, so I don't know how good that price is, but here's my advice…
Firstly: If you're using Paypal, make sure not to send money as Gift to Friends/Family. Sending as Payment for Goods protects you in case you never get the pin, or you get a counterfeit. IF THE PERSON YOU ARE BUYING FROM INSISTS YOU SEND AS FRIENDS/FAMILY, EVEN IF YOU OFFER TO PAY MORE TO COVER THE FEE YOURSELF, DON'T TRUST THEM.
Secondly: Don't forget, you can always ask someone for references. Chances are, if they have been trading or selling Disney pins for a while, they have accrued some, either on Dizpins Reference Center, here on DPF, or or eBay, and they can send you a link. I ask for references a lot if I'm trading or buying from a new person.
Best of luck, whatever you decide to do!