well since Luffy got only 3B bounty it is obvious that his crewmates will not got what they deserves either , and it is clear again that there is really no difference between Zoro and Sanji . Oda consider them as really nearly equals if not equals. the 1 million difference is for 2 reasons:
1. Sanji's usual pattern of having some repeated digits in his bounty
2. to make a joke later between him and Zoro about who has a higher bounty
Jinbe and Robin deserve their bounties too for different reasons Jinbe for his strength , Robin for her knowledge
Well Mihawk's bounty is deserved since he now is the strongest in a crew.
Crocodile must have gotten much stronger