I'm with Stefan on this one.
If I KNOW my item is worth 300, And I refust to let it sell for less than 250, then I would set my reserve for that (250) price. That way if it should be a slow week, or I forgot the entire country is away on vacation, I wont get burned by lack of interst when it only reaches 100 bucks.
And it IS true, when an auction starts out at a cheap start, it DOES get more bid action, and often will jump past where It might have been. I have seen pletny of auction where the start bid was too close to what I thought was the actual value, which ended with only one bid.