That's not bad. Shimiwaza is much worse.
What happens is that you have a couple of companies that are automatically setting the price of the book in response to the competition.
So one if one them drives up the price, the other moves to match it, then the first one increases the price again (this normally happens because the first company doesn't actually own the book, it's just planning to buy it from the second company, and send it on to you if you order it from them).
Details here: http://www.michaeleisen.org/blog/?p=358
Edit: I found a better example.