This is a very cool concept. Apple Stores in Japan sell “Lucky Bags” around the new year. It’s a tradition for Japanese retailers.
Apple also joins in. Most of the time, Lucky bags will cost a bit, but include items valued at more than the price you are actually paying for the bag. Say you buy one for $300, but it includes lots of goodies, such as an iPod, shirts, earbuds and more. A lucky few (hence the name) will get higher-valued items, such as an iPad or MacBook Air.
Shoppers buy these up in hopes of snatching an awesome surprise. Even if they don’t, the items in the bag are valued at enough to make the purchase worth it.