Sadly since Kim had to shut down people price his grips at 2 to 3 times original cost on the big auction site.
Of course it seems many if those priced in the $300 range don't move very quick.
I have several sets of K frame that were purchased over the years for $50 to $80. The few I have sold I usually asked $80 for because can't recall what I paid and don't want to be gouged so try not to do the same. But I don't sell those on open market. More of a friendly gesture to a Forum member.
Fairly I would say $150 tops but you can always start high and work down.