The fourth ed book hazard pay had a number of sample bounties on various threats (toxic shamans, blood mages, insect shamans, spirit beings). The bounties are offered by various groups for caught alive or killed and you can sometimes claim multiple bounties on one target. How much and what is ogfered depends on who and what.
At the low end you have an insect shaman who's killed 1 person and covered his tacks so he's low threat. They dont want him starting a hive but he's only killed one reporter so he for all his magical power which obviously makes him dangerous a trained and prepared group is expected to be able to bring him down. He has 3 bounties for his capture at 10k, 25k and 50k by knight errant, the FBI and ASPS.
Then you have things like the force 15 Wraith Maelstrom which has a 350k bounty for its destruction. Which has already elimated one exoedition sent to stop it.
Most are in the 150k range with the highest being a cycada shaman who originally worked for the CDC and stole a bung of infectious deadly diseases who has a 500k bounty for his capture.
Of.course these bounties are for splitting amongst the group.
In your case I'd say start by working out the base bounty using the formulas for prime runners in the 5th ed book. Then add extras on for various circumstances again as per standard e.g. Jaspar is a blood mage who's ben sacrificing the Sinless for his power.
Base Value = 3k
Highest die pool 12 = 3
Bounty: 9k split amongst the group for his death by KE
Sure he's a mage serial killer but he's targetting an area of the populace most don't care about and hes all alone. A nice easy starting bounty but you can modify it to change his value for example ...
He's more skilled die pool 15, has attracted a cult (outnumbered 2-1), is being actively hunted by his former corp for sharing their blood magic secrets), has been targetting upper class children as his sacrifices and has already wiped out a knight errant patrol.
Base Value: 3k
Die pool: 4
followers: 1
Vengence : +1
Closure:-10%
Atzlan HK team: +1
KE Bounty: 21k for death.
Parents of victims: 18,900k for death.
If they take him out they can claim both bounties for 39,900 and if they deal with the Atzlan team without killing them may even gain a little good will from the corp.
I'd say bounties you need to bring in alive are worth 10-20% more due to the difficultyin doing that
Bounties who have killed multiple teams sent after them are worth an extra 1.
Bounties who present a global threat (insect shamans, possess NBC weapons in addition to their own personal abilities or have demonstrated the ability to destroy entire towns) are +1.
Subjects who are especially good.at.covering their tracks are +1
And so on.