I think one factor that effects that is how fast the drop happens. I remmeber, when the price was around 450, then people used to say if it would go to 300, then they would buy 50K worth of bitcoins. But the drop was happening really fast, and a lot of them didn't. However the high 200 , and the low 300 does look like a stable bottom for now.
Rate of change definately plays a role, but IMO the reverse one.
If the drop happens rapidly, it is likely to be a panic-driven selloff that quickly rebounds = instant profit for those that buy the dip.
If, however, it happens slowly (like the current trend), it reflects people slowly losing faith and I would hesitate to buy at any level until there is some clear indication of a trend reversal.