Sorry, which event are you referring to?
Every year, WDW hosts the biggest pin event of the year at EPCOT, usually held around September. Since they change the theme every year, we tend to call it "the September event".
It's usually about $100 to go (this year it's $140), and you have to have a pass for EPCOT, as well. They hold it in a pavilion between Canada and the UK- someone once referred to it as "Iceland", which I thought was amusing.
Inside, you can trade, play pin trading games, that kind of stuff. They usually have an auction for lots full of AP/PP stuff, sometimes a trivia contest, etc. And every year, they release a ton of stuff for the event. Previously, it was mostly pins. But a few years ago, they added vinylmation (and eventually gave Sunday to vinylmation collectors all together, with a separate price tag). Last year, half of the catalog was other merchandise, which was a first. Things like t-shirts, statues, posters, etc.
The pin catalog usually comes before the event, so you can decide if you want to go. The have a random computer selection process (called the RSP) to do lottery-like drawings for who can buy what beforehand- we just submit what we want, and then they do the drawing to what you can buy. This keeps us from having to stand in long lines to get the harder-to-get stuff.
Here are the details:
http://www.disneyparksmerchandise.com/events/imagination-gala-trading-event/?instance_id=
