Whitebeard - WSM and has bounty 5,046,000,000
Kaido - WSC and has bounty 4,611,100,000
Mihawk - WSS, bounty - unknown
Three owners of the title of the WS. The bounty of the two are known. It is in the range of 4.5 - 5 billion.
Logically, Mihawk should have 4 billion or so.
But there is a nuance - no team. Although I am considering if you are strong, then you are strong without a team. BM, being only a kid and with one cook on her side, was already terrifying the countries of NW.
And if people were suddenly needed, then you can force them to obey and follow orders. If Hody managed to gather 100,000 people, then for BM it would not be difficult at all.
So I think the lack of a team is not such a big problem and does not greatly affect the bounty, if at all affects the bounty.
If Mihawk has a bounty of less than 3 billion, then his title of the Strongest is nothing compared to the titles of Kaido and Whitebeard.