I don't know ... I didn't expect anything less than ~ 2 Bil about Marco
maybe his bounty dropped after he lost a war and his crew?
Eh, no need for dropping his bounty, all WB pirates did was taking Ls since the beginning of the Marineford war, you don't get an increase by losing wars.
If Marco had 1,3 billion bounty at the beginning of the Marineford war then he won't get a bounty increase because he and his crew lost 2 wars in a row; Marineford War and Payback War against Blackbeard. Why should he get an increase by losing wars?
You need to either strategically win a war like this;
Or defeat someone who also has high bounties;
Marco did neither of these things during these two wars.
Blackbeard defeated Whitebeard and stole his DF power, and before that he defeated Ace (550 million), and then defeated Magellan.
Even Blackbeard didn't get 2.2 billion for doing these things, because he has 2 different wanted posters;
BB's First Wanted poster;
BB's Second Wanted poster;
Two different wanted posters.
So probably even Blackbeard was around 1 billion like Marco after the MF war. Despite defeating Ace, and Magellan, and even after killing WB and stealing WB's DF power, and even after wounding Fleet Admiral Sengoku, even BB was probably around 1 billion. He probably got 2 billion bounty only after defeating Marco.