"There are good examples in Bruce's database where a poster goes for $100+ and a few weeks later, the same poster in similar condition goes for $30."
Oddly though, there are also some where it goes the opposite way. It is all in who was there bidding that day. You want to be there the day Mr Deep Pockets is sleeping, or at the movies, and you can't predict that, so you want to bid $30 each time, knowing most times you will be blown away, until you finally get that $30 super bargain.
In this hobby, it is the PERSISTENT bird that catches the worm!
Bruce