People need to understand that Bounties aren't given based on Performance or Feats lol
From WG Perspective Three Captains defeated Two Yonko and then it gave Bounties to their Subordinates based on Fame, Importance and Hierarchy
Luffy, Law, Kid got 3 Billion
Usopp, Franky, Brook and Nami got 300M Boost Equally, since they are seen as Low Level Subordinates
Robin got 800M Boost due to being very important to WG and keeping her with a Yonko is so dangerous
Zoro, Jinbe and Sanji were given 1B Bounty due to being regarded as Luffy's Strongest Subordinates, the extra few millions were just a little addition from Oda to keep their numbers different
Killer also got a Bounty around 1.050B for sure
It doesn't matter who they fought or how they performed, WG simply gave The Captains 3B, Strongest Commanders 1B and Rest +300M
Robin and Chopper are only exception due to obvious reasons