I suppose it tracks that with law's and kid's defeat along with the strawhat's miraculous escape from egghead they would get a bounty increase. It does seem quite fast though. Maybe now his bounty will be comparable to the previous yonko, above 4 billion.
It would be the same with Dressrosa tho
Luffy's bounty was split with Law (500 million each), then Luffy's bounty increased to 1.5 billion
Luffy's bounty was also leveled with Law and Kid now (3 billion) each
1 billion for defeating Doflamingo, and 9 billion for defeating both Kaido and Big Mom is far more reasonable
So just like 1.5 was a more accurate representation of Luffy's level, so would a bounty of 4 or 5 billion