I just bought a K5ii for AUD 859 (USD 882) brand new. So they are obviously going pretty cheap wholesale now, too.
If you consider the sensor, even though it still compares very favourably to its competitors, is over 2 years old... with the pace these things move, it might not be long before it's significantly outclassed. My guess is that's what market sentiment would be, which would explain a) why they are going secondhand now b) why they are cheap new now c) why I bought one when normally I buy yesterday's papers for better value
and, one would surely think, d) why something Pentax put out at the $1500+ level ought to be on its way at some point.
On top of that... a lot of flighty people seem to be flocking towards full-frame options at the moment.