Honestly, meh, the whole concept of bounties is fucked up.
Whitebeard, a (relative) pacifist, who didnโt care about becoming PK, and didnโt even attack fodder marines has a higher bounty than Kaidou, whoโs one of the worst warmonger, wants to become PK, harbors a lunarian, knows about Joyboy, and has an ex scientist who worked for Vegapunk who has very dangerous fodder cleaning abilities, which endanger civilians, not to mention the brutal overall nature of the BP.
Ok sure, whatever. Truthfully, those 4 millions can mean anything, or even nothing.