It depends how it's pieced together,about 2k for a stock k24 bottom end/stock k20 head.
But then you need a transmission(1k),mounts(600),wiring harness(350),fuel system(500+),and miscellaneous other stuff(1k+).
Plus if you want to build the motor a little for more power,that's obviously going to cost more too.
If you have the money to go k series,go k series,just do it right.
__________________
"You can always count on the Americans to do the right thing - after they have tried everything else."
-Winston Churchill