You list it for a stupid price because you never know if someone is willing to pay a stupid price or not. One time I listed a sketch card from a different set for $1499.99. I figured it was a $700-$800 card at best. Someone offered $1300, and before I could even get onto eBay to accept the offer, they just hit the buy it now.
You never know what you can get, and no one wants to list low and always think they may have left money on the table. I've done that plenty of times, and now I just list for a stupid amount of everything, thats what the best offer feature is there for.