don't forget that there are different eeepc models, with different features and different prices.
the "eeePC" you linked to is a "4G surf" model. they cost less than the "4G' model because they have shorter battery life, and no webcam (neither feature matters if you're going to use it as a carPC).
the point is, $358 is not some awesome deal, it's just a cheaper model. eeePC prices are locked from ASUS, authorized retailers can't choose what they sell them for. the 4G surf sells for $349 everywhere. buy.com simply combined the selling price and shipping fee into one price (they claimed free shipping, but it's not free, it's $9 ).
BTW, 2G surf models sell for $299