I would appreciate if you learn two things.
1. Reading in english.
2. Typing in english.
1st point the most.
You literally have in the spoilers that Buggy's bounty is only this big because he is mistaken as the leader/creator of the Cross Guild in which Mihawk and Crocodile are.
Last chapter Law comments that having people as such is enough to make you a Yonko.
You don't need 30k fodders or irrelevant Commanders.
Crocodile is brains of the Cross Guild. He can fight but he ain't shit vs Top Tiers.
Mihawk is the heavy hitter.
That be 3.590b alone.
Still you are evuluating from your side. How did marine see this case ? You think marine said that
We know that buggy can not be real yonkou . Lets make gag and we can put high bounty ?
Marines see that Buggy is the former king pirates crew member , shanks buddy , impel down surviver , marineford war impacter and exwarlords with huge number of pirates group ( you know the number ? no ) . With this feats , they believed that he can control mihawk and crocodile .
I dont understand why you dont want to use your brain. You should understand you are reader . you know the what is happening in the manga and you expect that marines shoudl know what you know :))))))))))))))))))))))))))