In the past we went from $30 to $2, that is a factor of fifteen decrease. It was sparked by a hack at mtgox, but even before that the conditions were ripe for a bubble pop.
And here we are this week, down to $72 from $270. Again sparked by trouble at mtgox, but even before that the sheer speed of the increase in price and general mass hysteria indicated a bubble pop was coming.
History repeats itself.
$270/15 = $18. But this isn't an exact science so I will settle for a round $20.
Past performance is no an indication of future results.
It's impressive you've broken the entire bitcoin market just by dividing by 15 and rounding up to the nearest 20, but my dog thinks you're way off and he's predicting bitcoins will bottom out at 5 milk bones. I'm not sure who is right, but his estimate might be tastier, at least to him.