This would ruin pure pking, you already barely get any blood money for kills as a pure.. as the general risk is like 60-80k max.
Instead it should go off of combat levels, say level 88 would need a minimum of 76-120k risk, and 100-126 requiring 500-850k+ because the majority of PKing at 126 is either rune fighting or dharoking
Again excluding the untradable prices