The manager probably had just come off of his crack break. The $10 pre-sale box is the same as any other pre-sale package. It holds a copy of the game for you day of release and is a $10 credit towards the price of the game. ArenaNet has announced that the cost of Factions will be $49, and it is not an expansion. It is a stand alone game that interacts with the original Guild Wars.
More info can be found by reading their FAQ.
http://www.guildwars.com/aboutgw/faq/gu ... ns-faq.php