I picked up a lot of 20 pins on ebay for around $30. This is a random lot where you don't know what you are getting. These were supposed to be traders for my son. He quickly decided that ten of them were not traders.
Just bid what you think is fair. I decided that $1.50 per pin including shipping was what I wanted to pay. I lost all of the ten pin lots that I bid on. People were paying around $3.00 per pin. At twenty pins it took two auctions before I got one. The key is to not get attached to any particular auction and have someone else make you pay more than you want to.