I also feel this could completely ruin the economy with very minimal effort. Mbl and I discussed while building the map the plugin for mob bounties, and that there was no way to discern between naturally spawned mobs and spawner spawned mobs. Unless this has changed, this will allow you to kill many, many mobs at the same time. This would give everyone a substantial amount of money that even the current economy with the changing prices probably can't compensate for. If there's no way to distinguish between natural and spawner spawned, then it could pretty much guarantee that the map would need to be reset at the next update. That's not even taking into account what people could possibly sell the Diablo Drops tools and weapons at. (If they can be dropped from spawner spawned mobs)
The plugin knows the difference between natural spawns and spawner mobs
Yes, spawner mobs do not give money. mcmmo exp, or diablo drops, the only think you get are vanilla items and exp