I personally think that gold from killing demigods should be lowered (a bit), but the main issue is the gold assist distribution. For instance, if you kill a DG, the person who did the last hit will get the full cash cow, while potentially all the other players who tapped the dead DG prior to death will get half of that amount. Some math:
Case 1: 2 players gang up on one DG = $ (killing blow) + 0.5 * $ (assist) = 1.5 * $ (total)
Case 2: 5 players gang up on one DG = $ (killing blow) + 0.5 (assist ratio) * 4 (number of assisters) * $ = 3 * $
Twice the gold is handed out for killing the same demigod to the opposing team (another reason to always "hunt in packs"). Cash should be distributed in a different manner. I know that %damage dealed would mean %gold gained but this is hard to implement with heals/shields and other factors.
Maybe something in the whereabouts of:
$ = total cash gained from killing demigod (according to level)
Demigod dealing the killing blow = 0.33 * $
A demigod who dealt damage (includes killing blow dealer) = (0.66 * $) / NumOfDamageDealers
That way, for 900 gold bounty for killing a demigod by 3 players you would get:
Damage dealer = (0.66 * 900) / 3 = 200 per demigod
Killing blow will receive an extra 300 cash. Just an idea