Really woot? These are available on ebay for $1.00-$1.50 each shipped. Sure they may not be the "Apple" branded but they're the same thing. At nearly $10 each your price is a bit off the mark.
Actually not, there have been teardowns showing that many of the imitation chargers tend to be cheaply constructed, poorly functioning and in some cases dangerous. See this roundup, and optionally follow links to the teardowns for each product...
Of course, there's no guarantee the chargers being sold here are authentic either. There are counterfit versions that look virtually identical to the originals, and since these are in bulk packaging, there might be no way to tell for sure short of tearing them apart. And even if they are authentic, I agree that $20 is a bit much for a pair of USB chargers.