You know he became a warlord 10+ years ago right?
His bounty wont reach 1 .5 billion even
Coz he isnt even dangerous as crazy pirates
Mihawk frozen bounty is between 500 - 1.2
Or maybe he has no bounty who knows
Well sure, but Oda chose not to give the old bounties of the Warlords and made sure that they get into another inceident before their bounties are revealed
So as of now the frozen bounties aren't important... The bounties that matter are the ones they get After this initial Warlord man hunt... If Boa fends off the entire Fleet sent after her with the aid of her Nation, she'll get a bounty matching that... If Weevil fends off all the fodder going after him, his bounty might not increase, but if some strong vice admirals are part of that group then his bounty might increase...
And now for Mihawk, if theres only literally fodder after him, then his bounty won't increase... BUt if an admiral is part of the group after him then it gets interesting... If MIhawk destroys over 10 ships, and then beats like five top Vice admirals and then beats an Admiral too all in one incident... Alone... There's no way he can get a bounty below 1.5 billion
So i think it was intentional for Oda not to show any Warlord bounties last chapter because they are gonna be rescaled according to how well each Warlord does to escape thier capture and who they manage to escape from or defeat in the process