User blog comment:Sulahvardhan/Luffy.D.PIRATE KING/@comment-3569609-20121105065852/@comment-4754162-20121105075654

Sulahvardhan, you need to bear in mind that bounties were judged based on the information gathered by WG / Marines.

Zoro facing Kuma (in Thriller Bark) may not came to light, thus WG / Marines may not know about it.

Also, bounties were definitely NOT dependent on character's attack or skill, therefore bounty increased due to Red Hawk is not valid (WG / Marines may not even know what transpired in FI at all)