10 yen was a lot for the average Japanese to spend on a stamp in the early '50s, when Japan was still just beginning to recover from the depredations of World War II. It is likely that most of these stamps were simply used to pay the postage on parcels, and that many of the booklets collected were originally purchased by foreigners.
I've no doubt that Japan's economy will eventually rebound after having been hit by the recent horrific earthquake, tsunami, and nuclear disaster which caused so much devastation. Japan is the third largest economy in the world (after the U.S. and China), and has a large and active stamp collecting community. Furthermore, the Kannon booklet has worldwide appeal as a Buddhist Religion topical. There are hundreds of millions of Buddhists in the world, many of whom live in the rapidly developing countries of East Asia, and there is little doubt that Buddhist Topical stamps will grow in popularity over the long-term.
Note that these booklets are often found with minor condition problems, especially gum bends and perf separations. Try to buy a one that's clean and fault-free.