There exists an infinite number of fukubukuros. Some bags contain cosmetics, some bags contain famous designer name brand clothes, others games, depending on the stores.
The prices also vary significantly, but most bags are from the $10 to $100 range.
The big catch is, buyers must purchase the bag without knowing what is inside. And no returns and exchanges are allowed, even if you buy a fukubukuro at a favorite name brand fashion store and happen to get a pair of shoes you absolutely can't wear.
All fukubukuros are designed to provide good value to buyers. Most fukubukuros offer twice the value of the price, and sometimes even better. It's one of the convenient methods to control inventory for sellers. Therefore, every new year, Japanese rush to department stores looking for good luck and a better deal.
I am one of the people who never bought a fukubukuro. I was never lured by the idea of getting a good deal without knowing what I'm buying. I just can't understand the psychology of buying unknown items. I tend to think buying a fukubukuro is similar to buying a lottery ticket; a waste of money.
I thought fukubukuros only exist in Japan, but according to the Japanese language wiki, Apple stores have sold "lucky bags" at the grand opening of flagship stores since 2004 in the United States. Bundled subprime loans are also basically based on the same idea that are behind fukubukuros, as Toyo Keizai Online, a Japanese magazine writes in its article. You just don't know what you are buying.
So, Fukubukuros may not be an exclusively Japanese idea after all.