of course he is.
4 billion bounty is also very possible.
True but bounties are also pretty worthless now
Crocodile can stand his ground in the new world but only has had 80 million because he was an early villain
Moria jobbed not once, not twice, but a record-breaking three times in the series but his bounty is almost the same as Doffy's
The list goes on, but the general pattern is Early character --> lower bounty, later character ---> higher bounty
With a few exceptions of course, like Hancock
But the bounty hyperinflation mostly began in the New World; before that, 500 million was an ungodly amount (which people really thought it was at the time), but then the Yonko commanders and Yonko themselves completely broke the
financial system and caused the recession of 2008 broke the bounty balance to the point where strength of a character = size of their bounty is completely inaccurate in 80% of cases.