The 357PD is a rather rare bird. Took me over a year to find a good one. Pricing is hard to say, as they do not come up often from what I have seen. I paid $800 for mine about two years ago if that helps. They are no longer in production.
As smith said on the PD, they don't come up for sale very often and when they do will usually bring more than a .44 Magnum 329PD... The highest I've seen paid for a LNIB 357PD was just over a grand....usually they are in the $800-950 area.