People complain about books being too cheap, just like any other commodity. What about all the effort that goes into them? If price reflects quality, what do 99 cent books say about themselves?
I take a rather different view. For me, the low prices of some books act to lower what an economist would call the 'barriers to entry'.
A few days ago, for example, I came across the complete works of Jane Austen as a Kindle version -- 99 pence. At that kind of price, even if I'd never heard of Jane Austen, or if I wasn't sure I'd like her stuff, I would probably take a chance. After all, it's less than the price of a latte -- and will last quite a bit longer!
What's Amazon like from an author's point of view? See Why I like Amazon part 2: as an author.