The wiki page: http://www.ros.org/wiki/base_local_planner does not list the
units for the scoring parameters.

I'm assuming:
~<name>/path_distance_bias (double, default: 0.6) - meters
~<name>/goal_distance_bias (double, default: 0.8) - meters
~<name>/occdist_scale (double, default: 0.01) - Map obstacle cost (0-254?)

If this is the case, the default gains would yield roughly values all around
2 or 3, which would explain the very small value on obstacle cost.