We have gotten lots on ebay for as little as about 75 cents per pin. They were all official Disney pins (back-stamped with the Disney pin trading logo) and some were so cool we kept them for our own collection instead of trading them.
I just watch the lots until I find one I like and with the way they've gone lately, I don't buy anything that is over $1 a pin in a big lot. We usually trade around 100 pins on every trip and we only trade with CM's (we aren't THAT hard core - we just like to collect the ones we like!).
ETA: I may not be a hard core pin trader, but I do diligently try to purchase only official Disney pins. That said, we have always had excellent luck in getting official lanyard series pins for very cheap prices. I tend to buy from the same couple of sellers, so maybe that makes the difference - but I will respectfully disagree that if you are paying 80 cents a pin then you are getting "scrappers" because that has not been my experience at all. I'm not expecting limited edition or highly sought after pins for 80 cents each, but ones that are legitimately tradeable with CM's can be had for that price.
Edited again: So, I clicked the link in the signature - I guess I had a misunderstanding of what a scrapper was (I thought it was simply a non-Disney released pin). After reading the information about scrappers, then I suppose I could have inadvertantly purchased and traded hundreds of them. Both of the sellers I purchase from are located in Florida, however I was completely unaware of this "black market" of Disney pins. Oh my! I guess I'll buy in smaller lots from now on, but it doesn't appear as though the casual pin trader will likely ever be aware of whether or not their pin is a scrapper. Even the site says the only way you can be sure is to buy it from Disney - but I guess that rules out pin trading altogether. Thank you for bringing that to my attention though because it definitely never occurred to me.
One last edit: I can breathe easier because both of my most common sellers are on the "green" list. I can't swear how much I paid in those lots and I also can't swear I've never purchased from the "red" list - but I'm definitely more aware now.