Ten books by Amazon and Walmart, considering their size, is more a loss-leader than price war. The publicity alone, as mentioned in the article, is worth more than any losses. After the dust has settled, both their revenue and profit intakes will likely be up.
Prices for books move around more than I would have thought. I can understand the Amazon price drop on Stephen King as mention in the article because it was an analyzed move to compete with Wallmart. (price history graph: http://www.shopobot.com/under-the-dome-a-novel-hardcover)
