I think it is because people are trying to grab the ZDP Calys to make sure they will have the full set once they get the ZDP Delica and Jess Horn. Sort of how the first movie in a series sees a jump in sales right before the sequel comes out, or is released on DVD.
Personally, I think the ZDP Caly will drop WAY down in price once Spyderco and other companies release a few more knives in ZDP189. Years from now, I think the ZDP Caly won't be worth more than it's original street price and will be totally forgotten by collectors (though not users).
I used to want a ZDP Caly (well, I still do), but will not pay over $100 for it. I have now decided to stop looking and just wait for the ZDP Delica. I will not jump through hoops to get one either. And if I miss out, oh well, because one of my next knives is going to be a William Henry Titan in ZDP no matter what.