Don't worry, At that price, it's already gone.
That's exactly how I usually console myself. If you're not the first person to see these ads and show up at the person's house, then it's already gone before you can even get upset about it.
That's how I got my K1 for $250. A former member of the sohc4 group posted his bike for sale (this was back in the Greenspun message board days, so not nearly as much activity), and I jumped on it immediately, even though the bike was in Denver and I was in Oregon. Two days later I drove down in a friend's van and snatched it up!