Requested by ScottSpittle on dev bukkit:

I see you just updated to support MobArena. Any Chance you can add in a Reward ration?

For example MARation: 50
Means that they get only half of the normal Rate for killing mobs instead of the normal reward.

This is available in the current version as a Gain setting. For example:

Gain:
  MobArena:
    Amount: 0.5
    Share: false

The Amount is the multiplier so any coin reward will be cut in half (0.5). Also, the Share flag allows the reward to be shared with any other players in the same arena.