There are boards at the WDW huge yearly trade event (the one going on this weekend), and at the DSF ticketed trade events. Though the DSF boards tend to not have quite as many AP/PP pins on them in favor of leftover pins and PTDs from earlier releases.
If I pull an AP or PP off of the trading boards I usually give it away to a collector friend who collects and looks for those types. I, personally, do not value them any way different from the released pin. Just my opinion, but I can appreciate those who collect AP/PP's and I try to help out when I can.
I can appreciate AP/PP pins and I do get excited when I pull one off the trading boards. I think it's fun to turn over the pin and see that backstamp that indicates the pin is a little 'extra.' I understand that some people collect AP/PP pins as a separate category and/or treat them as separate versions of their released counterparts and value them differently.
I, however, don't value them differently (or consider them different) from the released pin unless the pin is VISIBLY different from said marketed version. That is, I need to be able to look at the pin and SEE that the AP/PP pin differs from the version that ultimately was sold in stores. If the only thing that differentiates an AP/PP pin from the released pin is the AP/PP backstamp, I won't value the pins differently. Just my opinion ... .