[ericcholis]

A few reasons:

1) It's from the Alpha set, the very first Magic Release. It's much rarer to find, since it wasn't as popular. http://www.mtgprice.com/sets/Alpha/Black_Lotus

2) It's graded a 9.5 out of 10 for it's condition. Practically perfect for an item that wasn't initially sought as a collectors item

3) The card itself is considered to be one of the Power 9, or some of the most powerful cards in the game. http://en.wikipedia.org/wiki/Power_Nine

Also, the card you linked is from the Unlimited set, which would be the 3rd printing of this card.