You don't make much because herbs never sell when they're cleaned (at least for the market price), but the bots get like 40-60k exp/hr hour, and that alone makes it worth being basically free.
another good place to do this would be at the dungeon place, seeing as there is no randoms there too ;] and go to world... umm 16 i believe? or whatever is the unoffcial effigies world, :3 gl and happy lvling