Hi and welcome to the forum!
Since you're new to this, you should understand that the special inserts (props, autographs, and most costumes) are NOT available in the packs you're buying at Suncoast or any other retail store. Artbox produced hobby and retail versions of the cards. The packs you're finding at retail stores are the retail version, which have ONLY two costume cards -- Harry's black robe and George's Quidditch robe.
Hobby boxes can be found at stores that carry non-sport cards, like sports card shops and comic book stores, online stores, and eBay. The stores may also carry the retail version. You have to read the packs. If it says that the pack could contain costumes, autos and props, then you've found the hobby version. If the packs say they could have random chase cards and costume cards (but don't mention autos or props), then they are the retail version.
There have been two releases for Prisoner of Azkaban -- the first set came out in May and the second set, called update, was released in November.
There is also a big difference in price between the two versions. Update hobby boxes cost around $60 and the packs can be $3.00 or higher. Retail boxes are about $40 and the packs are $2.00 or so. By the way, these packs aren't usually called booster packs. As I understand it, booster packs refer to gaming cards.
Hobby boxes for the update release can have 0-3 special inserts. Some people on the forum have been unlucky enough to get nothing but base cards and foils in a box. I think most people here agree that right now, you're better off buying the individual inserts you want.
For instance, you could spend well over $500 on a case of 10 boxes, and never pull a Hermione costume card. But if you go on eBay, you can find the trousers/pants card for $20-$25 and the UK exclusive robe for around $20 (not including shipping). That's a lot cheaper than buying a hobby box, plus you're guaranteed to get the card you want.
If you're looking for more detailed info about the cards and prices, go to the top of this page and click on the link for the price guide. A lot of people have spent a great deal of time entering eBay auctions so that we can all make informed decisions about how much to spend on the cards.
I won't slap you on the wrist about cherry picking, as T&F has already done that!
I think you'll find that most collectors abhor cherry picking, as it takes away the reasonable chance that someone buying a couple of packs will get anything but base cards. I'll bet that the reason you bought 200 retail packs and pulled only one costume is because someone cherry picked the packs before you found them.
Good luck finding the cards you want!
